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Edited by Roehlano M. Briones
Copyright 2021
Published by
Philippine Institute for Development Studies
Printed in the Philippines. Some rights reserved.
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ISBN 978-971-564-076-3 (softbound/printed version)
ISBN 978-971-564-077-0 (PDF/electronic version)
RP 01-21-600
v
Table of Contents
List of Tables, Figures, and Boxes ..................................................................................... ix
Foreword .............................................................................................................................. xv
Preface ................................................................................................................................xvii
Acknowledgment ............................................................................................................... xix
List of Acronyms ................................................................................................................xxi
Chapter 1
Irrigation and Agricultural Development .......................................................1
Arlene B. Inocencio and Roehlano M. Briones
Introduction ...................................................................................................................1
Rationale for Public Investment in Irrigation ...........................................................2
History of irrigation development in the Philippines..............................................5
Trends in irrigation development .............................................................................10
The irrigation development program of the Philippines: Key issues ..................29
Conclusion ....................................................................................................................34
Chapter 2
National Irrigation Systems .............................................................................. 36
Roberto S. Clemente, Arthur L. Fajardo, Vicente G. Ballaran Jr., and Julie Carl P. Ureta
Introduction .................................................................................................................36
Related literature .........................................................................................................38
Methodology .................................................................................................................40
Findings based on rapid appraisal .............................................................................43
Other analytical ndings ............................................................................................61
Conclusion ....................................................................................................................65
Chapter 3
Communal Irrigation Systems .........................................................................68
Roger A. Luyun Jr. and Dulce D. Elazegui
Introduction .................................................................................................................68
Background and Method .............................................................................................70
vi
Findings from IMO data ..............................................................................................75
Findings from System-level and IA-level Data ........................................................81
Recommendations .......................................................................................................94
Chapter 4
Water Resources Component ............................................................................ 97
Guillermo Q. Tabios III and Tomas Paolo Z. De Leon
Introduction .................................................................................................................97
Hydraulic modeling of irrigation canal network ..................................................104
Summary and recommendations ............................................................................116
Chapter 5
Irrigation Water Governance .........................................................................119
Agnes C. Rola, Therese R. Olviga, Francis John F. Faderogao, and Chrislyn Joanna P. Faulmino
Introduction ...............................................................................................................119
Irrigation water governance in the Philippines....................................................121
Results of the assessment .........................................................................................132
Conclusions and recommendations ........................................................................145
Chapter 6
An Assessment of the Free Irrigation Service Act ....................................149
Roehlano M. Briones, Roberto S. Clemente, Arlene B. Inocencio, Roger A. Luyun,
and Agnes C. Rola
Introduction ...............................................................................................................149
Implementation of free irrigation policy ...............................................................150
Related literature .......................................................................................................154
Method of the study ..................................................................................................159
Results and discussion ...............................................................................................161
Conclusion ...................................................................................................................171
vii
Chapter 7
Benet-cost Analysis of the Resurgent Irrigation System .....................175
Program of the Philippines
Roehlano M. Briones
Introduction ...............................................................................................................175
Background .................................................................................................................176
Methodology ...............................................................................................................184
Findings .......................................................................................................................190
Conclusion ...................................................................................................................197
Chapter 8
Assessing the Resurgent Irrigation Development ....................................199
Program of the Philippines: Synthesis Report
Arlene B. Inocencio, Albert Dale B. Inocencio, and Roehlano M. Briones
Introduction ...............................................................................................................199
Project identication .................................................................................................200
Project design and appraisal ....................................................................................207
Project implementation and procurement ............................................................212
System management and operations and maintenance .....................................214
Project monitoring and evaluation .........................................................................219
Concluding remarks...................................................................................................222
References ...........................................................................................................................225
The Authors ........................................................................................................................235
ix
List of Tables, Figures, and Boxes
Table
Chapter 1
1 Budget appropriation of the Department of Agriculture (DA) .............................11
for irrigation, in PHP millions (current prices)
2 Distribution of irrigation investments by type of project, system, and..............15
funding source, 1965–2016
3 PDP targets for irrigation, 2017–2022 .......................................................................30
4 Priority provinces of the Rice Industry Road Map 2030 ........................................33
Chapter 2
1 List of NIS cases covered in this report ....................................................................41
2 Problems with irrigation encountered by farmers ................................................52
3 Proportion of lined canals, Luzon and Mindanao systems (%) .............................56
4 PCA results for the integrated irrigation performance index ..............................65
Chapter 3
1 Status of irrigation development in the Philippines ..............................................73
2 Frequency distribution of CIS by the size of FUSA and technology type (%) .....75
3 Average cropping intensity of the CIS from the different IMOs visited .............77
4 Distribution of CIS IAs by category of functionality rating (%) ............................78
5 Deployment of irrigators development ofcers (IDOs) to CIS in .........................81
all the sample IMOs
6 Water delivery performance indices in all the IMOs visited ................................84
7 Water management practices in all the IMOs visited ............................................86
8 Silt and seepage levels in the canals of CIS for each IMO ......................................87
9 Performance on water distribution, maintenance of canals, and ........................90
maintenance of control structures in all the IMOs visited
10 Average rating of the individual indicators for IAs’ functionality ......................91
rating in 11 selected provinces in Luzon
11 Average rating of the individual indicators for IAs’ functionality ......................92
rating in four selected provinces in the Visayas
x
12 Average rating of the individual indicators for IAs’ functionality rating ...........92
in four selected provinces in Mindanao
Chapter 4
1 Monthly average releases to MWSS and AMRIS from Angat ..............................100
Reservoir (1996–2013) and NWRB allocation for NIA-AMRIS (in CMS)
2 Historical and watershed model computed daily ows of Angat ......................101
Reservoir inows, Ipo Dam local inows, Bustos Dam local inows, and
Umiray River ow diversions to Angat Reservoir (in CMS)
3 Results of hydraulic simulation for AMRIS north main canal ............................110
with inow of 14.6 CMS
4 Results of hydraulic simulation for AMRIS north main canal ............................111
with inow of 18.0 CMS
5 Results of hydraulic simulation for AMRIS north main canal ............................112
with inow of 26.65 CMS
Chapter 5
1 Institutions involved in irrigation water governance in the Philippines .........122
2 Irrigation project management activities of NIA and responsible units ..........125
3 Project management activities of NIA in NIS and CIS ..........................................127
4 Study sites ...................................................................................................................131
5 Irrigation water-related agencies and their roles in the irrigation ...................133
development cycle at the national level
6 Irrigation water-related agencies and their roles in the irrigation ...................137
development cycle at the meso level
7 Status of irrigation management transfer of NIS to IAs ......................................141
8 Participation of the CIS IAs in the planning and design stage ............................142
of the project cycle
9 Participation of CIS IAs in project construction ...................................................143
10 Participation of the CIS IAs in the M&E of system performance .......................144
Chapter 6
1 Basic responsibilities of NIA and IAs under various models ...............................151
of IMT contracts
2 Options for management and O&M payment........................................................158
3 Share of irrigation service fee in the cost of palay production ..........................162
by region, 2013 and 2017 (%)
xi
Chapter 7
1 Priority medium-yield provinces in the Philippines ............................................184
2 Investment costs of irrigation projects: Philippines, 2008–2015........................190
(PHP millions)
3 Estimated impact of irrigation: Philippines, 2008–2016 (PHP millions) ............191
4 Irrigated palay output (in ‘000 tons) and price (in PHP per kg), projections ...194
for 2017–2045: Philippines
5 Palay output and price, projections for 2017–2045, in PHP millions .................194
6 Palay output and price, projections for 2017 to 2045: Philippines .....................196
(in PHP millions)
Chapter 8
1 Criteria for selection and prioritization of NIA irrigation projects ...................201
under AFMA (%)
2 Status of project preparation activities ..................................................................208
Figure
Chapter 1
1 Theory of change for irrigation systems ....................................................................4
2 Public investments in irrigation, in PHP millions (2000 prices), 1965–2017 ......12
3 Irrigation investments by type of system in PHP billions .....................................13
(2000 prices), 1965–2016
4 Real irrigation investments by type of project, in PHP billions ...........................14
(2000 prices), 1965–2016
5 Average distribution of irrigated area by technology, 2015–2017 .......................16
6 Irrigated area by type of technology, ‘000 hectares (1967–2015) .........................17
7 Area irrigated by type of system, ‘000 hectares, 1964–2017 ..................................18
8 Average distribution of irrigated area by crop (%), 2015–2017 ............................19
9 Trends in irrigated palay production, area, yield, 1970–2017 ..............................20
10 Ratios of irrigated to total palay production and ...................................................21
area harvested, by region, 1970–2017
11 Yield advantage of irrigated over rainfed palay by region (%), 1970–2017 ........24
12 Trends in actual vs target irrigated area ..................................................................27
by type of project (new, restore, rehabilitation), 1990–2018
xii
13 Trends in irrigation intensities in NIS and CIS, 1965–2017 ...................................28
14 Shares in irrigation service area by operationality (%), 2010 and 2017 ..............28
Chapter 2
1 FUSA, program and actual irrigated areas, and ......................................................44
cropping intensities of selected NIS
2 Silted diversion dam of Dipalo River Irrigation System ........................................54
3 Missing gates in MalMar 2 River Irrigation System ...............................................57
4 Vaca Dam of Division 2, UPRIIS ..................................................................................58
5 Check gate with padlocks in Libmanan-Cabusao PIS .............................................59
6 Garbage near the gates of one section of Lateral B NMC, AMRIS .........................60
7 Erosion map for UPRIIS ...............................................................................................62
8 Groundwater map of Bukidnon and service areas of .............................................64
Manupali, Roxas-Kuya, and Pulangui RIS
9 3D map showing the relative elevation of the service area and terrain .............64
of the whole watershed of the NIS covered in Bukidnon
Chapter 3
1 Percentage distribution of communal IAs by functionality rating and ..............79
province in 11 sample IMOs in Luzon: 2014
2 Percentage distribution of communal IAs by functionality rating and ..............79
province in four sample IMOs in the Visayas: 2017
3 Percentage distribution of communal IAs by functionality rating and ..............80
province in four sample IMOs in Mindanao: 2017
Chapter 4
1 Angat Reservoir water resource system, including the .........................................99
Angat-Maasim River Irrigation System (AMRIS)
2 Pampanga Delta Irrigation System and its physical features .............................102
3 Long-term dependable (80%) daily ows over the ...............................................103
Lower Pampanga River (in m3/s)
4 Details of the Angat-Maasim River Irrigation System .........................................105
5 Details of the Pampanga Delta Irrigation System (PDRIS) canal layout ............105
6 Steps in hydraulic modeling of irrigation canal network ...................................106
7 View of irrigation canal network plan and prole data of main .......................107
canal, including irrigation service sub-areas at pertinent lateral outlets
xiii
8 North main canal (NMC) and lateral canals of AMRIS .........................................109
9 Sample graphical display of HEC-RAS computer model results .........................109
in a particular lateral canal of the of AMRIS canal network
10 Differences of simulated water elevations and bank elevations ........................113
at AMRIS north main canal with inow of 14.6 CMS
11 Simulated water depths at AMRIS north main canal ...........................................113
with inow of 14.6 CMS
12 Differences of simulated water elevations and bank elevations ........................114
at AMRIS north main canal with inow of 18.0 CMS
13 Simulated water depths at AMRIS North main canal ...........................................114
with inow of 18.0 CMS
14 Differences of simulated water elevations and bank elevations ........................115
at AMRIS north main canal with inow of 26.65 CMS
15 Simulated water depths at North main canal with inow of 26.65 CMS ..........115
Chapter 5
1 Service process model of the National Irrigation Administration .....................124
2 Management structure and ow of activities between NIA ofces ...................130
Chapter 6
1 Trends in the actual cost of O&M of rmed-up service .......................................152
areas, ISF collected of NIS: 1983–2016
2 Number and area of irrigated farms/holdings: Philippines, 1960–2012 ...........161
3 Cumulative distribution of net rice-producing households, 2015 (%) ..............163
4 Benets from free irrigation based on NIS IAs FGDs, percent of respondents ... 165
5 Reasons given for the change in O&M level, CIS IA respondents (n = 17) ........167
6 Share of NIA respondents by expectation of change in O&M with FISA (%) ....168
Chapter 7
1 Expenditures on irrigation in 2000 prices: ............................................................177
Philippines, 1965–2016 (PHP millions)
2 Irrigated area by system: Philippines, 1990–2019, (in ‘000 ha) ...........................177
3 Area harvested for palay by system: Philippines, 1987–2019 (in ‘000 ha).........178
4 Production (‘000 tons) and yield (tons per hectare) ............................................179
by system: Philippines, 1987-2017
5 Cost and returns by system: Philippines, 2002–2018 (in PHP per kg) ................180
xiv
6 Cropping intensity estimates by system: Philippines, 1990–2019 ......................181
7 Assessment frames for benet-cost analysis .........................................................189
8 Measures of project worth, irrigation investments, ex post: .............................192
Philippines, 2008–2016
9 Palay output (‘000 tons) and palay price (PHP per kg), base and .......................193
counterfactual case: Philippines, 2017–2045
10 Measures of project worth, irrigation investments, ex ante and .......................195
ex post: Philippines, 2008–2045
11 Measures of project worth, irrigation investments, ex ante and .......................196
ex post, xed change in irrigated area, Philippines, 2008–2045
Chapter 8
1 Public expenditures for irrigation, 1996–2016 (2000 prices) and number ........205
of NIA positions before and during the RatPlan
Box
Chapter 1
1 References to research reports from the assessment of the resurgent ................3
irrigation program of the Philippines by the Philippine Institute for
Development Studies
Chapter 2
1 Principal components analysis ..................................................................................40
xv
Foreword
It has been more than two years already since the Philippine government adopted
the radical policy of exempting farmers from payment of irrigation fees. Through
the passage of the Free Irrigation Service Act (FISA), the government has afrmed its
commitment to contribute to the lowering of the cost of production and further relieve
the farmers from the burden and consequence of unpaid irrigation service fees.
However, the passage of FISA is not a panacea for all the ills besieging the
Philippine irrigation system. For instance, a study by the Philippine Institute for
Development Studies (PIDS) found that while the beneciaries of the free irrigation
are poorer than average, a large majority of them are nonpoor.
To provide a basis for discussing the issues of the current irrigation policy
framework, PIDS compiles existing quantitative and qualitative studies that address
the technical, physical, and institutional aspects of the performance of the country’s
irrigation systems. This book focuses on the works done by the Institute in recent
years to assist the government in crafting reforms toward cost-effective irrigation
sector development.
The Institute hopes that this book will help inform the discussions on the
Philippine irrigation system and how it is managed, and thus contribute to the
objective of the country to create a more effective and sustainable irrigation system.
CELIA M. REYES
President
xvii
Preface
Irrigation has been part of the Philippine agriculture since precolonial times. Despite
changes in the policy framework governing the sector, irrigation has only become
more relevant. This is understandable given the rapid expansion of the Philippine
population, with corresponding increased pressures on the food supply. More crops
simply mean higher demands for irrigation water.
This has inspired us to come up with a book that zeroes in on the Philippine
irrigation system. This book features contributions from esteemed researchers from
various institutions and organizations, thus providing a comprehensive assessment
of the country’s irrigation development program. Hopefully, the assessment will
serve as basis for the policy reforms in the area.
We are indebted to the Philippine Institute for Development Studies for fueling
this project and providing us an avenue to share a wide variety of perspectives on
irrigation. This book is our humble contribution to the literature on irrigation,
particularly the national and communal systems and their entire project cycle.
While there has been a tremendous increase in the amount of public investments
in irrigation, the reality is that its development is still hampered by several issues.
This publication offers recommendations to address them.
The Authors
xix
Acknowledgment
This book has been years in the making. It began with the pioneering work of the
late Wilfredo David, former Chancellor of University of the Philippines Los Baños
and continued by the studies of Cristina David, former Senior Research Fellow of the
Philippine Institute for Development Studies (PIDS). Throughout, PIDS has overseen
this project, from the tenure of President Josef Yap, through to Gilberto Llanto, and,
currently, Celia Reyes. The Department of Budget and Management, under Secretary
Florencio Abad, funded the “Rapid appraisal of irrigation investments” under the
Zero-Based Budgeting Program Studies. Said project was headed by Cristina David
and Arlene Inocencio. Other contributors had authored articles on related studies,
including Miriam Nguyen, Tolentino Moya, Mona de los Reyes, and Alma de la Cruz.
Staff who at the time served as research assistants and associates had been
instrumental to these studies, including Cristina Alvarez, Cristeta Foronda, Alex
Baulita, Armand Christopher Rola, Joseph Daniel Sandoval, Jayson Fumera, Mae
Marie Garcia, Faith Villarma, Kristel Tapire, Arman Baulita, Kris Francisco, Francis
Quimba, Ivory Galang, and Isabel Espineli. Sheila Siar and the Research Information
Department Staff, especially Maria Judith Sablan and Gizelle Manuel, diligently
shepherded these studies to publication. Chito Madamba is the source of the striking
image for the book cover.
The National Irrigation Administration (NIA) has been unwavering in its support
of the PIDS evaluation studies from the 2000s up to the present, providing access to
its ofces, data, staff, and network of stakeholders, from NIA Central Ofce down to
its regional and eld ofces. The Authors are grateful to the stakeholders of irrigation
sector governance, especially the Department of Agriculture - Bureau of Soils and
Water Management, the National Economic and Development Authority, and, of
course, the farmers and operators of the various irrigators’ associations, for their
valuable time and insights on the state of the sector.
xxi
List of Acronyms
AFMA – Agriculture and Fisheries Modernization Act
AMM – asset management method
AMP – asset management plan
AMPLE – Agricultural Market Model for Policy Evaluation
AMRIS – Angat-Maasim River Irrigation System
ARMM – Autonomous Region in Muslim Mindanao
ASEAN – Association of Southeast Asian Nations
AWD – alternate wetting and drying
BAR – Bureau of Agricultural Research
BCA – benet-cost analysis
BCR – benet-cost ratio
BOT – board of trustees
BPW – Bureau of Public Works
BSWM – Bureau of Soils and Water Management
CAR – Cordillera Administrative Region
CARP – Comprehensive Agrarian Reform Program
CIDP – Communal Irrigation Development Project
CIP – communal irrigation projects
CIRDUP – Comprehensive Irrigation Research and Development
Umbrella Program
CIS – communal irrigation systems
CMS – cubic meters per second
CRA – Community Relations Assistant
DA – Department of Agriculture
DAR – Department of Agrarian Reform
DBM – Department of Budget and Management
DE – detailed engineering
DEM – digital elevation maps
DENR – Department of Environment and Natural Resources
DILG – Department of the Interior and Local Government
DP – Discussion Paper
EC – electrical conductivity
EIRR – economic internal rate of return
FAO – Food and Agriculture Organization
FGD – focus group discussion
FGIS – farmland geographic information system
FIELDS – fertilizer, irrigation, extension, loans for inputs
xxii
FISA – Free Irrigation Service Act
FMB – Forest Management Bureau
FS – feasibility study
FSSP – Food Staples Sufciency Program
FUSA – rmed-up service area
GIS – geographic information system
ha – hectare
HEC-HMS – Hydrologic Engineering Center - Hydrologic Modeling System
HEC-RAS – Hydrologic Engineering Center-River Analysis System
IA – irrigators’ association
ICC – Investment Coordination Committee
IDD – Institutional Development Division
IDMCs – irrigation and drainage management companies
IDO – irrigators development ofcers
IDP – Institutional Development Program
IfSAR – interferometric synthetic aperture radar
IMO – irrigation management ofce
IMT – irrigation management transfer
IPI – irrigation performance index
IROR – internal rate of return
IRR – implementing rules and regulations
IS – irrigation system
ISC – irrigators’ service cooperative
ISF – irrigation service fee
IWM – integrated watershed management
JICA – Japan International Cooperation Agency
kg – kilogram
KII – key informant interview
km – kilometer
LGC – Local Government Code
LGU – local government units
LPS – liter per second
m – meter
MAO – municipal agricultural ofce
MARIIS – Magat River Integrated Irrigation System
MASSCOTE – Mapping System and Services for Canal Operation Techniques
MAV – minimum access volume
MFN – most-favored-nation
MIMAROPA – Mindoro, Marinduque, Romblon, and Palawan
xxiii
NOAH – Nationwide Operational Assessment of Hazards
MOA – memorandum of agreement
MT – metric ton
MW – megawatt
MWSS – Metro Manila’s Metropolitan Waterworks and Sewerage System
NAMRIA – National Mapping and Resource Information Authority
NEDA – National Economic and Development Authority
NGO – nongovernment organization
NHC – National Hydraulic Research Center
NIA – National Irrigation Administration
NIMP – National Irrigation Master Plan
NIP – national irrigation project
NIS – national irrigation systems
NMC – north main canal
NPC – National Power Corporation
NWRB – National Water Resources Board
O&M – operations and maintenance
PCA – Principal Component Analysis
PCs – principal components
PDC – provincial development council
PDP – Philippine Development Plan
PDRIS – Pampanga Delta River Integrated System
PHP – Philippine peso
PIS – pump irrigation system
POWs – program of works
PRDP – Philippine Rural Development Program
PSA – Philippine Statistics Authority
QR – quantitative restriction
RatPlan – rationalization plan
RBCO – River Basin Control Ofce
RDC – regional development council
RIO – regional irrigation ofce
RIS – river irrigation system
ROW – right-of-way
RPMC – Regional Project Monitoring Committee
SDD – small diversion dam
SFR – small farm reservoir
SOCCSKSARGEN – South Cotabato, Cotabato, Sultan Kudarat, Sarangani,
and General Santos
xxiv
SSIS – small-scale irrigation systems
STW – shallow tubewell
SWAT – Soil and Water Assessment Tool
SWIP – small water impounding project
SWISA – Small Water Impounding System Association
TCP3 – Technical Cooperation Project 3
UPLBFI – University of the Philippines Los Baños Foundation Incorporated
UPRIIS – Upper Pampanga River Integrated Irrigation Systems
US – United States
USLE – universal soil loss equation
VEVA – Value Engineering/Value Analysis/Assessment
VIG – Variable Incentive Grant
WB – World Bank
WRDP – Water Resources Development Project
WRRC – water resource research centers
WTO – World Trade Organization
Chapter 3
Communal Irrigaon Systems
Roger A. Luyun Jr. and Dulce D. Elazegui
Introducon
Communal irrigation systems (CIS) are irrigation systems constructed by the National
Irrigation Administration (NIA) with inputs from farmer-beneciaries in various
phases of the project. These farmers are organized into irrigators’ associations (IAs)
that operate and maintain the irrigation system. CIS have service areas of less than
1,000 hectares (ha). They operate through either gravity system, where water level is
raised by a dam or a weir and water ow by gravity, or through a pump system, where
water is raised by mechanical action.
By virtue of the Agriculture and Fisheries Modernization Act of 1997, Local
Government Code (LGC), and Executive Order 718, series of 2008, IAs took over the
70 | Revitalizing Philippine Irrigaon
management of the completed CIS subject to a cost-recovery arrangement and
repayment scheme.
Most recently, however, the Free Irrigation Service Act heralded a new policy
milieu for CIS beneciaries and managers. Currently, IAs are receiving a subsidy from
NIA for their operations and maintenance (O&M).
While most CIS are constructed by NIA, several others started as private initiatives
and have received some government funding support for the cost of rehabilitation
and new construction. At least 95 percent of CIS are run-of-the-river type gravity
systems obtaining water from rivers or streams, though a few have been given
funding support for medium-sized pumps to also distribute water from a river.
Yields in CIS were lower by 30–40 percent than in the national irrigation systems
(NIS) because of the uncertainty in water supply in the small catchment areas where
CIS are located (FAO 2011). Unreliable water supply is a fundamental problem for CIS
tapping water from less dependable small rivers and creeks or relying on springs
and runoff.
The government has made huge investments in CIS, particularly around 1995-2010,
because more areas can be developed for CIS compared to NIS. Many CIS were found
to have service areas with slopes greater than 3 percent.
To expand the irrigation base, new irrigable areas may be served by small-scale
irrigation systems, including CIS (David 2003). As such, there is a need to assess the
status of CIS development in the country.
Background and Method
Issues raised in previous studies
While O&M problems affect individual users, the persistent problem in water
distribution is due not only to technical aspects but also institutional factors
governing water allocation. These relate to availability, reliability, predictability,
manageability, and equality of the allocation. The rst three relate to water rights.
Manageability refers to the combined control of users over the quantity and timing
of water deliveries. Equality refers to the sharing of benets commensurate to fees
paid and services rendered. The tail-end syndrome indicates the positional advantage
of upstream versus downstream due to topographic and conveyance conditions.
The unequal tenurial, social, and political status leads to differential access to
water (Cruz 1983).
70 | Revitalizing Philippine Irrigaon Communal Irrigaon Systems | 71
The involvement of farmers in planning the irrigation system is one important
factor in the existence of more functional canals and structures. Effective leadership is
crucial in addressing water distribution conicts between upstream and downstream
farms. A decentralized leadership solves coordination problems in CIS with widely
dispersed farms (de los Reyes and Jopillo 1986).
The management structure of CIS becomes more formal as system size increases.
More successfully managed systems divide their areas into smaller units or sectors for
broader involvement of farmers in managing the system and more organized distribution
of water. The interventions of NIA in the IAs, such as in areas of organizational structure,
leadership, and systems management, yielded positive impacts. These include higher
productivity, stronger associations, improved water distribution, and better compliance
with government policy (de los Reyes and Jopillo 1986).
Government investments in irrigation also suffer from political pressures, rent-
seeking, and corruption perpetuating technical and economic inefciencies in the
irrigation and water sector (Wade 1982; Repetto 1986; Araral 2005a; Huppert 2013).
Problems of sustainability of irrigation infrastructure include overestimation of
benets during the planning stage of the project. The area estimated to be served by
the irrigation system is generally much larger than what is served. Projected yields
are also overestimated although water use efciency declines over the years. Another
cause is the lack of investments in recurrent costs associated with O&M activities once
construction is completed (Ostrom 1990). Donors normally restrict their involvement
in the design and construction and view O&M as the responsibility of the recipient of
the system. Routine maintenance is delayed until the deterioration of the system is
large enough to require rehabilitation.
A wide range of factors causes the poor performance of irrigation systems,
spanning from technical aspects to institution-related issues. Constraints may
be rooted in the inadequacy of relevant data during the planning stage, errors in
design, poor quality of construction, and lack of institutional capacity for system
development. Moreover, the complex operation and socioeconomic and institutional
management of an irrigation system, and the inadequate support services for irrigated
agriculture make it difcult to fully achieve potential performance (David 2003).
Design shortcomings of CIS include errors in estimating design oods and sediment
loads of rivers, lack of head control structures, ungated intake structures, and faulty
design of farm ditches. The rate of deterioration at 140,000 ha per year of both NIS
and CIS between 1996 and 2004 casts doubt on the sustainability of irrigation systems
in the country (UPLBFI 2007).
72 | Revitalizing Philippine Irrigaon
Development of CIS in the Philippines
CIS covered approximately 663,000 ha, accounting for 35 percent of the total area
served by irrigation systems in the country in 2017 (Table 1). The development of
irrigation system lags in Mindanao, considering the large irrigable area, relative to
Luzon and Visayas.
Construction of simple irrigation systems dates to the Spanish era when
mountain tribes built the Ifugao rice terraces and Spanish friars installed systems
in areas bordering Manila. Farmer associations were building, operating, and
maintaining irrigation systems (World Bank 1990). A set of practices referred to as
the Zanjera system ensured that farmer-beneciaries participate in the maintenance
of the system (de los Reyes and Jopillo 1986). Zanjeras are known for their capacity
to manage gravity-fed CIS and for their rules and regulations, water allocation and
distribution, system O&M, and conict resolution (Yabes 1990).
Under the American regime, an Irrigation Division was created in the Bureau
of Public Works (BPW) in 1908. The legislature provided for the regulation of water
rights and conceptualization of IAs for managing CIS. With the destruction brought
by World War II, BPW provided assistance to both NIS and CIS.
Foreign nancing of CIS projects came in the 1970s as a component of rural
development projects. The rst foreign-assisted project in the Philippines focusing
mainly on CIS and beneciary participation was the Communal Irrigation Development
Project (CIDP) in 1982. By 1983, all NIA-assisted communal irrigation projects were
adopting the participatory approach. The involvement of farmers in the planning of
CIS project and the incorporation of their suggestions in the design contributed to
more functional canals and structures (de los Reyes and Jopillo 1986).
The second CIDP project was implemented in 1990 (World Bank 1992a). NIA
obtained loans from the International Bank for Reconstruction and Development
and International Fund for Agriculture and Development. The four components of
the project were construction and rehabilitation of CIS, development of communal
IAs, institutional development of NIA on communal irrigation, and agricultural
development planning.
By virtue of the LGC of 1991, CIS were devolved to local government units (LGUs),
including similar projects funded by municipalities, provinces, and cities. Prior to the
enactment of the Code, NIA implemented locally funded CIS with a budget allocation
of PHP 518 million under the General Appropriations Act. In 1992, the fund for CIS
implementation was transferred to the internal revenue allotment of the LGUs. As
72 | Revitalizing Philippine Irrigaon
Esmated
Total Irrigable
Areaa/
Service Area (hectares) Share in Total
(%)
Total
Remaining
Area to be
Developed
Naonal
Irrigaon
System
Communal
Irrigaon
System
Private
Irrigaon
System
Other
Government
Agency
Assisted
Total
CAR 111,295.65 15,936.64 55,293.89 23,376.34 3,606.82 98,213.69 88.25 13,081.96
Region 1 264,491.00 61,499.44 57,519.40 20,788.45 50,575.83 190,383.12 71.98 74,107.88
Region 2 457,246.76 176,273.28 54,734.49 44,501.34 21,021.12 296,530.23 64.85 160,716.53
Region 3 483,830.18 219,165.30 75,964.06 9,343.65 19,481.79 323,954.80 66.96 159,875.38
Region 4A 85,929.00 29,034.00 22,778.00 7,288.00 2,553.00 61,653.00 71.75 24,276.00
Region 4B 143,558.95 29,130.59 39,372.92 14,973.91 12,596.00 96,073.42 66.92 47,485.53
Region 5 239,440.00 24,016.05 74,613.04 25,059.00 15,966.30 139,654.39 58.33 99,785.61
Region 6 191,253.16 53,935.08 39,035.13 15,309.81 15,012.30 123,292.32 64.47 67,960.84
Region 7 53,674.35 12,210.99 31,510.00 4,068.00 1,496.00 49,284.99 91.82 4,389.36
Region 8 91,982.90 25,877.00 38,573.90 5,915.75 2,765.00 73,131.65 79.51 18,851.25
Region 9 93,706.00 19,049.59 25,826.15 1,957.00 3,481.00 50,313.74 53.69 43,392.26
Region 10 121,122.69 32,164.82 29,072.05 4,930.54 4,784.25 70,951.66 58.58 50,171.03
Region 11 177,546.92 38,567.98 29,267.33 1,291.00 1,675.27 70,801.58 39.88 106,745.34
Region 12 293,226.24 71,299.41 39,756.18 2,840.00 10,256.00 124,151.59 42.34 169,074.65
Region 13 160,176.75 32,029.70 28,672.00 3,137.00 6,418.00 70,256.70 43.86 89,920.05
ARMM 160,150.45 27,712.86 21,241.75 90.00 295.00 49,339.61 30.81 110,810.84
Total 3,128,631.00 867,902.74 663,230.28 184,869.79 171,983.68 1,887,986.49 60.35 1,240,644.51
* as of December 31, 2017
For provinces with service areas greater than the estimated total irrigable area, it means that more areas are now irrigated beyond the estimated total
irrigable area.
Note: CAR. Region 7, Region 8, Region 9, Region 10, Region 13, and ARMM generated 13,963 ha. of new areas but not yet operational. CAR = Cordillera
Administrative Region; ARMM = Autonomous Region in Muslim Mindanao
Source: NIA (2017b)
Table 1. Status of irrigaon development in the Philippines*
74 | Revitalizing Philippine Irrigaon
a result, the construction and rehabilitation of CIS by NIA in areas where concerned
LGUs had no capacity to undertake CIS projects had been stalled. Since 1992, NIA has
implemented CIS in partnership with farmer-beneciaries through their IAs, which
contributed a portion of the direct cost during construction.
Data collection
The performance of CIS was examined at two levels: (1) NIA irrigation management
ofces (IMOs) and(2) IA level. The analysis was based on secondary data, mainly from
NIA, provincial IMOs, and key informant interviews (KIIs) with staff, and primary data
from eld investigation of selected CIS and focus group discussions with IAs.
Technical data included physical state, service area, irrigation efciency, source
of water, access to and availability of water, year constructed, and start of operations,
cropping calendar, and cropping intensity. Field investigation included walk-
throughs and actual measurements for a subset of sample CIS to gauge the physical
conditions of the systems.
Institutional data included the status of IAs, such as prole/institutional report
of IAs, their source of funding, nancial status and viability, program of works for all
available years, and CIS performance.
The assessment was done in two cycles. Cycle 1 covered Luzon while Cycle 2
covered Visayas and Mindanao. The system-level analysis covered 66 sample CIS
and IAs in 11 selected IMOs in Luzon (six each from Laguna, Ilocos Norte, Cagayan,
Isabela, Nueva Vizcaya, Benguet, Pangasinan, Nueva Ecija, Pampanga, Camarines
Sur, and Occidental Mindoro); 12 sample CIS and IAs in four IMOs in the Visayas
(three each from Leyte, Iloilo, Capiz, and Bohol); and 12 sample CIS and IAs in four
IMOs in Mindanao (three each from North Cotabato, South Cotabato, Davao del Sur,
and Bukidnon).
To capture possible differences in characteristics, selection of CIS per
province was based on size of rmed-up service areas (FUSA) in hectares:
(1) small (50 ha and below), (2) medium (between 50 and 100 ha), and
(3) large (above 100 ha)—considering one for each size category. Depending on
groundwater potential, at least one pump irrigation system (PIS) was also selected for
the provinces considered.
74 | Revitalizing Philippine Irrigaon Communal Irrigaon Systems | 75
Findings from IMO data
Firmed-up service area
Based on FUSA, most CIS were small (below 50 ha) gravity systems. A fth were only
partly operational.
Table 2 shows the frequency distribution of CIS based on the size of FUSA, type of
technology (gravity or pump), and operational status in the sample IMOs for Luzon,
Visayas, and Mindanao. Over 40 percent of 1,606 CIS under the 11 sample IMOs
in Luzon and 464 CIS in four sample IMOs in the Visayas had FUSA below 50 ha
(small) while over 50 percent had 50 ha and above (medium to large). In contrast,
85 percent of the 176 CIS in the four sample IMOs in Mindanao had medium to
large FUSA.
Majority of CIS had run-of-the-river type gravity irrigation systems, except in
Cagayan, Isabela, and Camarines Sur, where more than 50 percent of the systems
were PIS. There were no PIS selected in Leyte and no actual CIS using pumps in the
selected provinces in Mindanao. Farmers with shallow tube wells (STWs) sourcing
water from shallow aquifer systems acquired them through their own initiatives or
from other government agencies. Some CIS were also in rice areas with slopes greater
than 3 percent, particularly in areas outside NIS, such as the Upper Pampanga River
Integrated Irrigation System (UPRIIS) and Magat River Integrated Irrigation System
(MARIIS). Just over 10 percent in Luzon and Visayas used pumps.
Table 2. Frequency distribuon of CIS by the size of FUSA and technology type (%)
Island
Group
FUSA (ha) Technology Extent of Operaon (%)
Small
<50
Medium
50-100
Large
>100
Gravity Pump Others1≤50% > 50 Others2
Luzon 41.10 25.59 33.31 79.64 17.81 2.55 4.73 74.84 20.42
Visayas 46.55 31.90 21.55 86.42 12.5 1.08 11.64 78.45 9.91
Mindanao 14.77 36.36 48.86 100 0 0 11.36 87.5 1.14
1 not classied
2 partially operational/ongoing/deferred/not yet operational
CIS = communal irrigation system; FUSA = rmed-up service areas; ha = hectare
Source: Authors’ data obtained from respective IMOs (Luzon data as of 2013 and 2014; Visayas and Mindanao
data as of 2017)
76 | Revitalizing Philippine Irrigaon
Over 70 percent of all CIS in Luzon and Visayas and 87 percent in Mindanao were
above 50 percent operational. In Luzon, around 20 percent were partially operational,
or ongoing, deferred, or not yet operational systems. Meanwhile, around 5 percent
were below 50 percent operational due to defective/inadequate facilities. Partially
operational, ongoing, deferred, or not yet operational CIS were more notable in Ilocos
Norte, Bulacan-Neva Ecija, and Cagayan-Batanes. Nonoperational CIS were reported
higher in Occidental Mindoro and Isabela. The causes of these conditions were
discussed in the technical review based on the walkthroughs of the sample systems.
Cropping intensity
CIS maintained an average cropping intensity above 130 percent, though a signicant
proportion (especially in Visayas and Mindanao) fell below this threshold.
Cropping intensity is the ratio of area irrigated to the FUSA (or design area in some
cases) of CIS. Annual cropping intensity could also be the ratio of area irrigated
during the dry and wet seasons to the area irrigated during the wet season expressed
in percentage. According to NIA Camarines Sur IMO, cropping intensity should
be at least 130 percent, i.e., 100 percent for wet and 30 percent for the dry season.
The national average cropping intensity dropped from 133 percent in 2013 to
129 percent in 2014. In 2017, the national average cropping intensity based on FUSA
was 144.5 percent (NIA 2017).
The average cropping intensity of all CIS in all IMOs visited are shown in
Table 3. In the selected 11 IMOs in Luzon, the average annual cropping intensity of CIS
was 158 percent, higher than the national average.
Of the total 1,151 CIS reported by IMOs, 81 percent had cropping intensity
higher than 130 percent, indicating they were better than the national average. The
average cropping intensity was slightly higher in Mindanao (160%) than in Luzon
(157%) and the Visayas (158%). Among the sample IMOs in the three regions, Visayas
had the least percentage of CIS with cropping intensity above 130 percent.
Functionality of CIS IAs
Majority of CIS IAs achieved at least a satisfactory rating in terms of functionality.
NIA conducts functionality assessment of CIS IAs based on parameters related to O&M
performance, nancial performance, and organization and organizational discipline.
76 | Revitalizing Philippine Irrigaon Communal Irrigaon Systems | 77
Table 3. Average cropping intensity of the CIS from the dierent IMOs visited
Average Cropping Intensity Value (in %)
Luzon 158
Visayas 157
Mindanao 160
Percentage of systems:
Luzon
Below 130 percent cropping intensity 12
Above 130 percent cropping intensity 81
Data not available 7
Visayas
Below 130 percent cropping intensity 22.6
Above 130 percent cropping intensity 64.0
Data not available 13.4
Mindanao
Below 130 percent cropping intensity 24.4
Above 130 percent cropping intensity 73.3
Data not available 2.3
CIS = communal irrigation systems; IMO = irrigation management ofce
Source: Authors’ data obtained from Seasonal Operational and Maintenance Report of respective IMOs
(Luzon data as of 2013, 2014; Visayas and Mindanao data as of 2017).
Results of the annual or seasonal functionality surveys are used in the search
for outstanding IAs at the provincial, regional, and national levels. This is a good
motivation for IAs and their members. It also helps NIA in identifying appropriate
strategies to enhance IA’s capabilities. The rating is done through discussions and
consultation with IAs and relies heavily on reports provided by irrigators development
ofcers (IDOs), who are NIA staff focused on community organizing.
Currently, indicators and the percentage weight used in rating functionality of
IAs include:
• O&M 35
• Financial performance 26
• Organization and organizational discipline 29
• Assistance program/agri-support services/linkages 6
• Special features 4
O&M indicators include O&M planning, implementation, and performance,
such as annual cropping intensity, irrigated area vis-à-vis programmed area, status
78 | Revitalizing Philippine Irrigaon
of irrigation facilities and structures, yield, and collection efciency. Financial
performance includes income generation and fund utilization, and viability index.
Organization and organizational discipline cover information on membership,
meetings, recording/ling system, attendance in meetings and group work, holding
of regular elections, conict resolution, and the imposition of discipline. The overall
score indicates the following functionality rating:
• Outstanding (O): 95–100 percent
• Very satisfactory (VS): 85–94 percent
• Satisfactory (S): 75–84 percent
• Fair (F): 65–74 percent
• Poor (P): below 65 percent
Table 4 shows the distribution of CIS IAs in all sample IMOs based on functionality
rating. A majority (around 76%) of IAs in 11 sample IMOs in Luzon, as well as in the
Visayas, had satisfactory to very satisfactory ratings. Around 19 percent of IAs in
sample IMOs in both regions had fair to poor ratings. In Mindanao, over 16 percent of
IAs in the sample IMOs were outstanding and over 14 percent had fair to poor rating.
Table 4. Distribuon of CIS IAs by category of funconality rang (%)
Area Outstanding Very
Sasfactory
Sasfactory Fair Poor
Luzon 4.30 34.25 42.12 15.04 4.30
Visayas 4.86 45.14 29.86 17.36 2.78
Mindanao 16.47 47.65 21.18 7.65 7.06
CIS = communal irrigation systems; IAs = irrigators’ associations
Source: Authors’ data obtained from respective IMOs
On a per IMO basis, IAs in Isabela, Nueva Vizcaya, and Pampanga-Bataan had
very satisfactory ratings. Fair to poor ratings, on the other hand, characterized IAs
in Laguna-Rizal, Occidental Mindoro, and Camarines Sur during the wet season (the
province had seasonal functionality survey during the period (Figure 1).
78 | Revitalizing Philippine Irrigaon Communal Irrigaon Systems | 79
Figure 1. Percentage distribuon of communal IAs by funconality rang and
province in 11 sample IMOs in Luzon: 2014
0
10
20
30
40
50
60
70
80
Percentage (%)
Outstanding
Very
Satisfactory
Satisfactory
Fair
Poor
*Functionality survey is done only once a year except in Camarines Sur where it is done every wet and dry season.
IAs = irrigators’ associations; IMO = irrigation management ofce
Source: Authors’ data obtained from functionality survey reports of respective provincial IMOs (as of
2013 and 2014)
In the Visayas, 80 percent of Bohol IAs had very satisfactory ratings. In contrast,
majority of IAs in Iloilo and Capiz were rated as fair and satisfactory, respectively.
Only Leyte had IAs with poor ratings (Figure 2).
Figure 2. Percentage distribuon of communal IAs by funconality rang and
province in four sample IMOs in the Visayas: 2017
0
20
40
60
80
100
Bohol Leyte Iloilo Capiz
Percentage (%)
Outstanding Very Satisfactory Satisfactory Fair Poor
IAs = irrigators’ associations; IMO = irrigation management ofce
Source: Authors’ data obtained from functionality survey reports of respective provincial IMOs (as of 2017)
80 | Revitalizing Philippine Irrigaon
In Mindanao, all IAs in South Cotabato had very satisfactory ratings, with over
40 percent of them rated as outstanding. Poor IAs were noted in North and South
Cotabato, and Bukidnon (Figure 3).
Figure 3. Percentage distribuon of communal IAs by funconality rang and
province in four sample IMOs in Mindanao: 2017
0
20
40
60
80
100
Bukidnon Davao del Sur North Cotabato South Cotabato
Percentage (%)
Outstanding Very Satisfactory Satisfactory Fair Poor
IAs = irrigators’ associations; IMO = irrigation management ofce
Source: Authors’ data obtained from functionality survey reports of respective provincial IMOs (as of 2017)
Deployment of irrigators development ofcers (IDOs)
NIA’s ability to coordinate with and support IAs was limited by inadequate stafng of IDOs.
Table 5 shows the number and deployment of IDOs to CIS in each of the selected IMOs.
The role of an IDO is very crucial to IAs’ institutional development. Based on KIIs with
IDOs and Institutional Development Division (IDD) ofcials, the IDOs’ workload was
quite heavy. For instance, most of the IMOs in Luzon had fewer than 10 IDOs with
some assigned to both CIS and NIS projects. There were 68 gravity CIS and 28 pump
CIS in Pampanga, and four were under preconstruction. There was one senior IDO for
CIS and one community relations assistant. In Pangasinan, the supervising IDO was
the overall supervisor for both NIS and CIS IDOs. There were IDOs assigned to CIS in
six districts.
As of writing, IDOs still had heavy loads but were not getting adequate incentives,
such as security of tenure and other benets. In the Visayas, one IDO was assigned 14
to 20 CIS. IDOs in Mindanao had a lighter load with one IDO in charge of three to eight
CIS.
80 | Revitalizing Philippine Irrigaon Communal Irrigaon Systems | 81
Table 5. Deployment of IDOs to CIS in all the sample IMOs
IMO No. of CIS/IAs No. of IDOs
Luzon
Pampanga 68 1 Senior IDO for CIS and 1 Community
Relaon Assistant (CRA)
Nueva Ecija 60 7 IDOs with CRAs helping
Pangasinan 120 8 IDOs are assigned to CIS in 6 districts
Ilocos Norte 116 4 IDOs assigned to CIS; 5 IDOs to both CIS/
NIS; 2 farmer/irrigator organizers
Benguet 431 3 IDOs
Camarines Sur 152 2 IDOs for CARP and SRIP; 6 Research
Assistant B posion covering 5 districts
Nueva Vizcaya 217 4 IDOs are assigned CIS/IAs
Isabela 45 1 assigned to CIS project but there are
many radiaon projects
Cagayan 673 3 IDOs
Laguna 13 3 IDOs in 3 districts
Occidental Mindoro 32 5 IDOs
Visayas
Bohol 213 14
Leyte 186 13
Iloilo 123 7
Capiz 62 3
Mindanao
Davao del Sur 77 10
South Cotabato 35 10
North Cotabato 68 12
Bukidnon 40 14
IDOs = irrigators development ofcer; CIS = communal irrigation systems; NIS = national irrigation systems;
IAs = irrigators’ associations; IMO = irrigation management ofce; CARP = Comprehensive Agrarian Reform
Program; SRIP = Small Reservoir Irrigation Project
Source: Authors’ data obtained from respective IMOs
Findings from system-level and IA-level data
This section presents results of the survey of 66 sample IAs in 11 selected provinces in
Luzon in Cycle 1 and 12 sample IAs each in both Visayas and Mindanao. Information
include the technical assessment of CIS and institutional assessment of IAs.
82 | Revitalizing Philippine Irrigaon
Technical assessment of CIS
Location
The scope of irrigable area in the country was probably wider than
current estimates.
The slope maps showed that some CIS were irrigating rice areas with slopes
greater than 3 percent, particularly in areas outside large NIS like UPRIIS and MARIIS.
In some cases, CIS were irrigating small patches of areas under a 3-percent slope. The
3.1-million hectare-potential irrigable areas as dened by NIA based on the 0-3 percent
slope were quite low. There is a vast potential for small-scale irrigation development
if a good surface water source is present or if it is underlain by a good aquifer. This
lends credence to a World Bank study, which included areas up to 8-percent slope
increasing the irrigable areas to more than 6.1 million ha. These show that the basis
for the delineation of potential irrigable areas should be revisited.
Water sources and availability
The lack of surface water during dry season was a key constraint in
CIS performance.
In the feasibility study stage of a typical CIS, historical records of river discharge
are subjected to hydrologic frequency analysis using the 80-percent dependable ow
in the design. In the absence of data, engineers usually rely on empirical equations,
such as rational equation and other site-specic case studies, water balance methods,
or synthetic data generated using hydrologic models, such as the Hydrologic
Engineering Center - Hydrologic Modeling System (HEC-HMS) and the Soil and Water
Assessment Tool (SWAT). The reliability of these methods should always be tested
and the results calibrated with actual data.
The water sources for the surveyed CIS included lakes, rivers, creeks, springs,
groundwater, and runoff or a combination of one or more sources. Rivers, creeks,
and springs were the major sources of irrigation water in Luzon. Groundwater was
particularly used in Pampanga, Isabela, and Laguna. In the Visayas, only one sample
CIS in Bohol used groundwater as an additional source. In the Mindanao sample
CIS, rivers were the only water source in Davao del Sur while other provinces had
either springs or creeks as other sources. Except for some large rivers, there were no
historical records of the discharges of the river and creek sources for CIS.
Only 29 out of the 90 (30%) CIS visited had river sources deemed capable of
providing irrigation even during dry seasons. Seven of these rivers are very large and
82 | Revitalizing Philippine Irrigaon Communal Irrigaon Systems | 83
provided water for large NIS as well. If the CIS is sourced from these rivers, dry season
crops are assured of irrigation 80 percent of the time, and only siltation and hardware
problems are left to deal with. However, the majority of CIS were sourced from less
dependable small rivers and creeks, as well as springs and runoff (rainfall excess),
which did not even have historical records of ows that can serve as a basis for
sensible engineering designs. In these cases, the source of water is a major problem.
This was compounded by environmental problems, such as denuded watershed cover
due to logging and kaingin and land use conversion, among others. Moreover, the ow
records showed that even during the 1970s, the minimum measured ows were way
below the mean daily discharge. This indicates that even larger rivers, in some cases,
may not be able to supply irrigation during the dry season.
Many parts of the country had extensive and productive aquifers which can be
tapped as supplementary sources of irrigation water.
Adequate groundwater was found in parts of Isabela, Pampanga, Pangasinan,
Ilocos Norte, Laguna, Leyte, Iloilo, Davao del Sur, and North and South Cotabato.
Meanwhile, localized productive aquifers were present in Cagayan and other parts of
Isabela, Camarines Sur, Benguet, and Occidental Mindoro, Bohol, Leyte, Iloilo, Capiz,
Davao del Sur, and North and South Cotabato. For Benguet, localized perched aquifers
were the sources of springs. Bohol, on the other hand, has many springs due to the
karst formations underlying the province. On the other hand, Nueva Vizcaya and
Nueva Ecija were without signicant or limited pumpable groundwater, particularly
since the visited CIS were located on the outskirts of the Pampanga River Basin.
Water delivery program
Based on IA self-assessment, the implementation of the CIS water delivery
program was satisfactory.
Water delivery performance indicators include exibility, reliability, and
equitability (Table 6). Flexibility refers to the ability of CIS to deviate from an
established irrigation schedule. Based on farmers’ perception, the average exibility
index was computed at 3.3 in Luzon and 3.7 in both Visayas and Mindanao. This
indicates that the exibility was quite high. The highest was 4 in Benguet, Bohol,
Capiz, Davao del Sur, and North and South Cotabato, and the lowest was 1.5 in Nueva
Ecija. The lowest in Mindanao was in Bukidnon at 2.7. Most of the interviewed IAs
had dened schedules for water releases, especially during the dry season when
water is limiting, but is rather exible during the wet season when water is more
than sufcient. Some IAs had strict rules and penalties for noncompliance or water
84 | Revitalizing Philippine Irrigaon
stealing. Flexibility in larger irrigation systems may be limited by the lack of control
structures to divide or divert ows between zones.
Table 6. Water delivery performance indices in all the IMOs visited
IMO Flexibility Index Reliability Index Equitability Index
Luzon (average) 3.3 3.5 3.7
Pampanga 3.8 3.2 3.7
Nueva Ecija 1.5 3.2 3
Pangasinan 3.7 3.5 3.8
Ilocos Norte 3.3 3.2 3.8
Benguet 4.0 3.8 3.8
Camarines Sur 3.2 3.8 3.7
Nueva Vizcaya 4.0 3.8 4.0
Isabela 3.0 3.6 3.8
Cagayan 3.0 2.8 3.3
Occidental
Mindoro 2.7 3.8 3.8
Laguna 3.7 3.3 4.0
Visayas (average) 3.7 3.7 3.7
Bohol 4.0 4.0 4.0.
Leyte 3.7 3.7 3.7
Iloilo 3.0 3.0 3.0
Capiz 4.0 4.0 4.0
Mindanao (average) 3.7 3.7 3.5
Davao del Sur 4.0 4.0 4.0
South Cotabato 4.0 4.0 4.0
North Cotabato 4.0 4.0 4.0
Bukidnon 2.7 2.7 2.0
IMO = irrigation management ofce
Source: KII with ofcers/members of irrigators’ associations (IAs)
Reliability is an expression of condence by the irrigation system to deliver
water as promised (Murray-Rust and Snellen 1993). It is also the degree to which the
irrigation system conforms to prior expectations of its users (Rao 1993). The average
score for Luzon based on the KIIs was a high 3.5. However, it was higher at 3.7 in
both Visayas and Mindanao, indicating reliable water delivery. Some farmers were
resigned to the fact that water is scarce during a certain dry period to the point they
would not receive water. As such, they usually nd other water sources, such as
84 | Revitalizing Philippine Irrigaon Communal Irrigaon Systems | 85
STWs or low-lift pump. The almost uniform rainfall distribution in Mindanao and the
reliable water sources in both Visayas and Mindanao were plus factors.
Equitability, referred to as equity in some literature, is the spatial uniformity of
the ratio of the delivered amount to the required amount (Molden and Gates 1990).
It is also an expression of the share for each individual or group considered fair by
all system members (Murray-Rust and Snellen 1993). Based on KIIs, the average
equitability index score in Luzon and Visayas was also high at 3.7 and a bit lower in
Mindanao at 3.5. This means that the members considered the distribution of water
among members per IA as equitable. Most IAs interviewed practiced downstream rst
irrigation scheduling during the dry season. Flexibility, reliability, and equitability
of water delivery was not a problem in Benguet because all CIS were sourced from
springs and mountain rivers. Water is also stored on a series of storage tanks and
distributed to individual patches of lands with the use of high-density polyethylene
hoses. The reliability of water source was the main reason for the high index ratings
of CIS in Bohol, Capiz, Davao del Sur, North Cotabato, and South Cotabato.
Water management practices
Water management practices, such as alternate wet-and-dry and reuse of
drainage water, were adopted in majority of CIS.
The lack of proper water management practices, both by the farmers and the related
agencies, has been identied as one of the reasons for the low irrigation efciency.
To enhance such low irrigation efciency, it is suggested that capacity development
and the introduction of new water-saving technologies be required. IAs were also
asked how they conserve water or cope with expected water decits. Specically,
they were asked if they practice alternate wetting and drying (AWD) or if they reuse
drainage water for irrigation. In Luzon, 27 out of 64 (42%) IAs said they practiced AWD.
Meanwhile, 6 out of 12 (50%) IAs in the Visayas and 9 out of 12 IAs (75%) in Mindanao
practiced AWD. IAs learned the technology by attending training conducted by the
Philippine Rice Research Institute or the International Rice Research Institute and
sponsored by NIA. In Benguet, AWD was not applicable because the crops planted
were not rice. Only 10 percent of IAs in Luzon reused drainage water for irrigation.
Meanwhile, this was again higher in the Visayas and Mindanao, at 50 percent and
83 percent, respectively. Other IAs had no idea whether they practice AWD or
drainage reuse or not. Table 7 shows the result of the KII.
86 | Revitalizing Philippine Irrigaon
Table 7. Water management pracces in all the IMOs visited
IMO Praccing AWD Reusing Drainage Water
Yes No Ye s No
Luzon 27 37 6 56
Pampanga 5 1 2 2
Nueva Ecija 1 5 0 6
Pangasinan 2 4 0 6
Ilocos Norte 2 4 0 6
Benguet 3 3 3 3
Camarines Sur 4 2 0 6
Nueva Vizcaya 0 5 0 5
Isabela 2 3 0 5
Cagayan 3 3 0 6
Occidental
Mindoro 2 4 0 6
Laguna 3 3 1 5
Visayas 6 6 6 6
Leyte 2 1 0 3
Iloilo 3 0 3 0
Capiz 1 2 0 3
Mindanao 9 3 10 2
Davao del Sur 3 0 3 0
South
Cotabato 3 0 3 0
North
Cotabato 3 0 3 0
Bukidnon 0 3 1 2
IMO = irrigation management ofces; AWD = alternate wetting and drying
Source: KII with ofcers/members of IAs
Sedimentation and silt control
Many CIS were rated by their IAs as being heavily silted.
The IAs from Pangasinan, Camarines Sur, Bohol, North Cotabato, South Cotabato,
and Bukidnon rated their silt level as high, which veried the observations from the
walkthroughs (Table 8). Silt levels in canals were also high in Nueva Vizcaya, but the
values assigned by IAs were relatively low. Members in these areas conducted regular
cleaning of canals since CIS canals were small and did not require renting a backhoe,
unlike that in NIS. Heavy siltation was mostly observed in the dams of most systems
86 | Revitalizing Philippine Irrigaon Communal Irrigaon Systems | 87
during the walkthroughs. IAs also reported relatively high undesired seepage,
primarily because most them still wanted all their canals to be concrete-lined.
The provision of silt control devices was not included in the CIS design manual
of NIA. However, several silt control devices were encountered during the eld visits,
all of which were observed in Mindanao. This is quite understandable given that the
catchment management program of the Water Resources Development Project (1998)
was piloted in Mindanao.
Table 8. Silt and seepage levels in the canals of CIS for each IMO
IMO Silt Level Grade Undesired Seepage Grade
Luzon (average) 1.7 2.7
Pampanga 1.5 2.8
Nueva Ecija 1.8 3.8
Pangasinan 3.0 2.7
Ilocos Norte 1.3 2.5
Benguet 0.8 3.7
Camarines Sur 3.3 2.0
Nueva Vizcaya 0.7 2.0
Isabela 1.5 2.8
Cagayan 1.7 2.5
Occidental Mindoro 2.7 0.5
Laguna 0.6 4.0
Visayas (average) 1.3 3.6
Bohol 3.3 3.3
Leyte 0.0 4.0
Iloilo 2.0 3.0
Capiz 0.0 4.0
Mindanao (average) 2.8 2.7
Davao del Sur 0.0 0.0
South Cotabato 4.0 4.0
North Cotabato 4.0 4.0
Bukidnon 3.3 2.7
Note: For silt level grade, the ratings go from 0 = low to 4 = high. For Undesired seepage grade, the ratings
go from 0 = high to 4 = very low seepage
CIS = communal irrigation systems; IMO = irrigation management ofce
Source: KII with ofcers/members of IAs
88 | Revitalizing Philippine Irrigaon
Design considerations
Shortcomings in system design complicated subsequent O&M.
The CIS dams are mostly run-of-the-river types with simple designs, such as
ogee-type or glacis spillways, gated weirs, and gabions. Some dams are quite old, with
exposed rock cores, damaged spillways, or silted storage area. Most of the dams visited
had sediments almost at the crest level. These would require dredging to increase the
storage capacity and increase water available for irrigation. Large-scale silt problems
that will require the use of backhoe need the assistance of NIA.
The sluice gates are used to control the water level at the dam and ush out
sediments preventing it from entering the intake gates, which control the amount of
water entering the system. Most of the sluice gates and intake gates usually made of
steel were replaced with ashboards, sandbags, or stones. In one CIS, the steel sluice
gates were not even installed. In some relatively larger CIS, the lifting mechanisms
were defective or rather slow. IAs in Visayas and Mindanao resorted to using second-
hand or rented chain blocks to facilitate lifting and closing the gates. These gates
should be repaired or replaced to ensure proper control of the water and sediment
intake.
Since CIS have small FUSA, infrastructure costs are more for canal linings and
control structures. Most of the CIS visited had lined main canals while some have
lined canals up to the laterals. The conditions of the lined and unlined canals depend
primarily on whether the IA have good O&M and cleanup activities. Siltation was a
major problem but usually, the IA can manage to clean the canals themselves
Since the discharge capacity was small, only simple structures were found in
most CIS. While some were well maintained, others have deteriorated and the control
structures were not functioning well as originally intended. These included cross
regulators, check gates, drop structures, division boxes, and farm turnouts. Cross
regulators were found only in the main canals of some large CIS while check gates
were more common on small main canals and laterals. In most new CIS, the steel gates
were still in good condition and the screws and turning wheels were still operating.
In older and improperly managed CIS, the gates were already damaged and replaced
by wooden slabs or, in some cases, none.
Drop structures are ubiquitous in all systems and are lined to prevent channel
scouring and erosion. They are often combined with check gates and division boxes
to minimize costs. Division boxes are also usually made of concrete with slots for
wooden slabs, which serve as control gates. The control of ow direction is done by
88 | Revitalizing Philippine Irrigaon Communal Irrigaon Systems | 89
the water master based on agreed upon irrigation schedules. The density of farm
turnouts depends on the FUSA of CIS. Together with the check gates, it inuences
the exibility and efciency of water delivery within the system. Only four CIS had
digitized maps of their system and some of the maps did not indicate the kind of
structures present in the system. Some CIS had inverted siphons channeling water
under roads or rivers. Most of these structures have been rehabilitated or desilted
already. Still, some were under request for repair. Elevated umes can also be found
in some CIS.
There were no ow measuring structures. Any form of ow measurement was
done at the headworks, but these were only based on staff gauge readings and rating
curves, most of which have not been recalibrated since the CIS construction. Other
miscellaneous or appurtenant structures commonly found in all CIS included road
and thresher crossings, end checks, and service roads. IAs generally regarded poorly
the availability of roads along canals. Most service roads were rough roads with most
dams accessible only by walking or by motorcycle, which added more cost to the
farmers to deliver their harvest to rice mills and storage facilities. One of the main
requests of IAs was the provision of farm-to-market roads to ease this burden.
There were no specic drainage canals at CIS. Normally, the downstream farm
ditches receive the excess water from paddies, sometimes used to irrigate downstream
areas. In most systems, water distribution downstream was from paddy to paddy,
without individual farm ditch for each paddy. Again, the downstream canal serves as
the drainage canal. These are done to maximize areas devoted to planting. However,
the absence of drainage canals more often contributes to ooding or a longer time for
ood recession.
Maintenance
Based on IA self-assessment, maintenance of CIS was rated as mostly satisfactory.
As shown in Table 9, most IAs regarded the water distribution as more than
satisfactory with an average rating of 3.2 in Luzon, 3.5 in Visayas, and 3.4 in Mindanao.
The results also showed that the canals and control structures were deemed well
maintained, indicating the management and policy implementation of the individual
IAs themselves. A major contributing factor was the small size of CIS, which makes
them easier to manage and maintain, even with the occurrence of high siltation in
the canals.
90 | Revitalizing Philippine Irrigaon
Table 9. Performance rang on water distribuon, maintenance of canals,
and maintenance of control structures in all the IMOs visited
Province Water Distribuon Maintenance of
Canals
Maintenance of
Control Structures
Luzon (average) 3.2 3.1 2.9
Ilocos Norte 2.7 3.0 2.0
Pangasinan 3.0 2.8 3.0
Cagayan 2.7 2.8 3.0
Isabela 3.2 3.5 2.8
Nueva Viscaya 2.7 2.8 2.8
Pampanga 3.7 3.3 3.5
Nueva Ecija 3.5 3.7 3.2
Camarines Sur 3.3 3.2 3.2
Laguna 4.0 3.4 3.6
Occ. Mindoro 3.2 2.7 2.5
Benguet 3.0 2.8 2.8
Visayas (average) 3.5 3.3 3.4
Bohol 4.0 3.0 3.0
Leyte 4.0 4.0 4.0
Iloilo 3.0 3.0 3.0
Capiz 3.0 3.0 3.3
Mindanao (average) 3.4 3.4 3.3
Davao del Sur 4.0 4.0 4.0
South Cotabato 3.7 3.7 3.7
North Cotabato 3.0 3.0 3.0
Bukidnon 2.7 2.7 2.3
Note: 0 - Very Poor; 1 – Poor; 2 – Average; 3 – Satisfactory; 4 - Excellent
IMOs = irrigation management ofces
Source: KII with ofcers/members of IAs
Institutional assessment of IAs
Performance indicators
Based on specic indicators of functionality, IAs in Luzon were getting relatively
lower ratings on O&M and nancial indicators, compared to organization and
organizational discipline.
On average, majority of the provinces had IAs far from the 40-percent score in
O&M and 30 percent in nancial performance. IAs had scores closer to organization-
90 | Revitalizing Philippine Irrigaon Communal Irrigaon Systems | 91
related indicators (Table 10). In the Visayas, only Iloilo got an overall fair rating. Its
IAs had the lowest average score in the different indicators, except in organizational
discipline where it was highest. Leyte had the highest rating in O&M, Capiz in nancial
performance, and Bohol in assistance program and linkages (Table 11). In Mindanao,
only Davao del Sur got an overall rating of outstanding, securing the highest score in
O&M and nancial. Other provinces’ IAs also did well with a very satisfactory rating.
Bukidnon was the highest in linkages (Table 12).
Table 10. Average rang of the individual indicators for IAs’ funconality
rang in 11 selected provinces in Luzon
Province (Rang) O&M
(40%)
Organi-
zaon
(15%)
Financial
(30%)
Organi-
zaonal
Discipline
(15%)
Average
Scores in
addional
indicators
Final
Rang
(Total)
Pampanga (S) 30.88 12.67 24.69 12.89 2.58 83.71
Nueva Ecija (S) 30.90 12.75 20.91 12.24 3.79 80.62
Pangasinan (S) 32.58 12.25 18.40 12.48 6.16 81.87
Ilocos Norte (S) 32.87 14.21 20.58 14.69 7.72 82.95
Camarines Sur (S) 29.45 13.37 19.67 13.71 3.25 79.42
Nueva Vizcaya (VS) 34.60 12.85 22.10 12.39 3.76 85.69
Isabela (VS) 35.47 13.03 21.09 12.67 2.79 87.83
Cagayan (S) 32.51 12.43 19.35 13.26 5.50 83.05
Laguna (F) 27.96 11.05 17.49 11.48 4.12 72.10
Occidental
Mindoro (F) 23.18 11.54 21.38 11.40 4.50 72.00
ALL (S) 31.04 12.62 20.57 12.72 4.42 81.16
IA = irrigators’ association; O&M = operations and maintenance
Source: Authors’ data obtained from functionality survey reports of respective provincial IMOs (as of
2013 and 2014)
Coping strategies and assistance received
The IAs have adjusted to the limited water access through various coping
strategies with support from NIA.
Over 48 percent of IAs in Luzon reported problems related to water access in
terms of quantity and timeliness of delivery. This was related to the operation and
92 | Revitalizing Philippine Irrigaon
management of the system, as well as access to funds needed for rehabilitation.
Similarly, access to funds needed for rehabilitation, followed by O&M, was raised by
the majority of IAs in the Visayas. In Mindanao, access to water and access to funds
were equally important issues to IAs. O&M and access to credit were likewise cited by
majority of IAs.
To supplement irrigation water supply particularly during dry spells, 34 percent
of IAs in Luzon used STWs, low lift pumps, or deep wells, but the members did this
Table 11. Average rang of the individual indicators for IAs’ funconality
rang in four selected provinces in the Visayas
Province
(Rang)
O&M (35%) Financial
(26%)
Organi-
zaonal
Discipline
(25%)
Assistance
Program/
Linkages
(10%)
Special
Features
(4%)
Final Rang
(Total)
Bohol (VS) 31.33 22.00 22.67 9.00 2.33 88.33
Leyte (VS) 35.07 23.50 22.76 8.67 2.37 91.58
Iloilo (F) 28.40 17.12 23.53 4.40 0.35 73.80
Capiz (S) 31.20 24.50 22.77 4.67 1.67 84.80
ALL (S) 31.50 21.78 22.93 6.68 1.68 84.63
IA = irrigators’ association; O&M = operations and maintenance; VS = very satisfactory; F = fair; S= satisfactory
Source: Authors’ data obtained from functionality survey reports of four IMOs (as of 2017)
Table 12. Average rang of the individual indicators for IAs’ funconality rang
in four selected provinces in Mindanao
Province (Rang) O&M
(35%)
Financial
(26%)
Organiza-
onal
Discipline
(25%)
Assistance
Program/
Linkages
(10%)
Special
Features
(4%)
Final
Rang
(Total)
Davao del Sur (O) 34.50 24.00 28.55 6.00 3.50 96.55
North Cotabato (VS) 33.53 18.43 27.07 5.50 3.75 88.27
South Cotabato (VS) 32.05 21.25 24.35 4.90 2.63 85.18
Bukidnon (VS) 32.07 22.33 22.90 7.50 2.28 87.08
ALL (VS) 32.99 21.28 25.57 6.10 3.04 88.95
IA = irrigators’ association; O&M = operations and maintenance; O = outstanding; VS = very satisfactory;
Source: Authors’ data obtained from functionality survey reports of four IMOs (as of 2017)
92 | Revitalizing Philippine Irrigaon Communal Irrigaon Systems | 93
individually. The other 25 percent adjusted water scheduling or practice rotational
irrigation, while another 18 percent planted alternative crops, such as corn, mung
bean, or watermelon. The rest of IAs did nothing to cope with a dry spell. In the
Visayas, majority planted alternative crops but 33 percent did nothing. In Mindanao,
majority resorted to pumps, STWs, deep wells; adjusted water scheduling or practiced
water rotation; or practiced AWD. Other IAs also planted alternate crops.
IAs that rated high performance cited the following good practices:
• resourcefulness of IA president in generating funds, such as through Balik
Tangkilik (patronage refund) from selling to the National Food Authority
and assistance from government programs, such as the Comprehensive
Agrarian Reform Program (CARP), and international projects;
• coordination of IA with the barangay council to adopt the IA policy,
such as water distribution, for enforcement of policies through a
barangay resolution;
• strong cooperation of IA members in the strict implementation of the
provisions of by-laws, such as payment of IA fees, imposition of penalties
for absence in meetings and violation in water scheduling, no receipt, no
water, and rst-come, rst-served basis in water delivery;
• effective nancial management to ensure funds for O&M and loan
repayment, incentives for early payment of fees, and income-generating
activities, such as equipment rental, selling farm inputs, and crop
diversication; and
• regular cleaning of dam and main canals, including trimming of the grasses,
before the start of the rainy season. They also avoided using herbicide
which they fear could contaminate irrigation.
Of 66 IAs interviewed in Luzon, 51 reported getting continuous support from
NIA. By province, Ilocos Norte, Cagayan, and Laguna had the least number of IAs
with support from NIA. Assistance from NIA included the use of equipment and other
services, such as desilting. All IAs in the Visayas and Mindanao reported that NIA
provided them continuous support.
Majority (80%) of IAs in Luzon, Visayas, and Mindanao rated NIA assistance as
excellent in terms of technical, nancial, and institutional aspects, among others.
Technical assistance included rehabilitation of the system, concreting of canal and
construction of irrigation facilities. Meanwhile, nancial assistance primarily came
from LGUs and politicians. Institutional assistance included training and capacity-
building activities. Other services included lending of heavy equipment. Other
94 | Revitalizing Philippine Irrigaon
agencies providing assistance as cited by IAs in Luzon, Visayas, and Mindanao
included the Department of Agriculture (DA) and its attached agencies, such as the
Bureau of Soils and Water Management (BSWM).
Recommendaons
Irrigation planning and feasibility
The scope of potential irrigable areas for CIS needs to be widened. However, other key data must
be obtained to properly delimit areas suitable for irrigation.
Three criteria are proposed for identication of potential areas for CIS. The
rst is to consider all areas with up to 8-percent slope, minus the built-up and other
protected areas. This will serve to widen the scope of potential irrigable areas for CIS.
The second criteria should be the presence of a dependable surface water source and a
good shallow aquifer, which may be used as a supplemental water supply. Hydrologic
data acquisition and monitoring should be improved and expanded to smaller rivers,
creeks, and groundwater. Empirically derived ows should also be reviewed, with
special consideration on the effect of climate change. There should be a concerted
effort among concerned government agencies, such as the National Water Resources
Board, NIA, BSWM, and the academe to identify potential sites for diversion dams
and storage reservoirs. The third criteria should be soil texture and its suitability to
different types of crops, which would support crop diversication.
Addressing low water availability
The practice of supplementing irrigation from surface sources with groundwater from STWs should be
encouraged, especially in areas where surface water sources, such as creeks, have very low dependable
discharges during the dry season and for areas underlain by good shallow aquifers.
While using STW pumps and engines incurs additional fuel costs, they do provide
a reliable water source during intense drought periods or El Niño episodes. Moreover,
farmers have control of irrigation schedules and ows, enabling some of them to
increase cropping intensity or diversify into other crops. Some NIA IMOs have already
installed standby STWs, which they only use during periods of prolonged droughts.
94 | Revitalizing Philippine Irrigaon Communal Irrigaon Systems | 95
Farmers’ initiatives in deployment of STWs should receive stronger support from DA
and NIA.
To address low irrigation efciency, IA capacity development and the introduction of new
water saving technologies and cropping practices should be promoted and/or sustained.
In CIS where the dry season ow cannot support anymore the dry season
irrigation requirements, various options are still available to IAs. These include
reliance on water-saving technologies like AWD and adjustment of cropping practices
for rice, such as direct seeding to minimize water use from land soaking and land
preparation. IA may also consider crop diversication like planting nonrice crops or
crops requiring less water, particularly in areas at the tail-end of the system.
Another option that needs to be given greater consideration is the adoption of piped
irrigation systems.
Common suggestions raised by IAs to address problems in their systems usually
refer to physical measures, including lining of canals and rehabilitation of irrigation
systems or structures. Generally, rehabilitation connotes lining of canals. However,
the concreting of canals is impractical if the soil is clayey. With the availability of
low-cost, high-density polyethylene pipes, it is about time to look into the feasibility
of using these materials for subsurface canals, instead of concreting open channels to
convey irrigation to the elds.
Currently, such piped systems are seldom considered in system design owing to
high investment costs. A more sophisticated trash rack or sediment control at the
intake is also needed to prevent clogging. Drain holes and repair vents are also needed
at key locations in the systems, which again increase the investment cost. Other
problems may be rat infestation, which may cause further clogging of the system and
destruction of rice crops.
Nonetheless, the high initial cost and other disadvantages may be offset by
several benets, including:
• lower O&M cost due to reduced rubbish and sediments in the system;
• increased areas for planting as the canal is buried underground and risers
are used to distribute water to farm ditches;
• lower costs for right-of-way acquisitions;
• reduced seepage and percolation losses; and
• easier water control in terms of command and ow.
96 | Revitalizing Philippine Irrigaon
Lastly, piped systems are easier to modify to install sprinkler systems, thereby
facilitating crop diversication should IAs seek to move out of rice monoculture.
Addressing siltation and other technical issues
Design modications of CIS are needed to anticipate water shortages and siltation.
Provision for rotational irrigation should also be incorporated in the design of canal
system, with more checks or control gates for more efcient water distribution.
Drainage should be taken into consideration in the design criteria to avoid gross
underestimation of on-farm water losses.
In the case of rehabilitation work, existing systems must be checked for design shortcomings,
such as underestimation of ood ows and sediment loads, inadequate provisions for sediment
control, and underestimation of reservoir inow and outow hydrographs.
Generally, the dams and control structures should be properly maintained and
repaired to ensure proper water control and distribution. The dam storage area should
be regularly cleared of sediments to increase storage capacity and extend irrigation
even with diminished river ows. This should be part of regular O&M activities of the
IAs. If heavy equipment is necessary, NIA should extend help to IAs.
