Conference PaperPDF Available

Environmental Impact of Newly Built Tanks System Under the Moragahakanda-Kaluganga Re-Settlement Programme

Authors:

Figures

Content may be subject to copyright.
49
Environmental Impact of Newly Built Tanks System Under the
Moragahakanda - Kaluganga Re-Settlement Programme
V.K.N. Sameera 1 and M.P. Perera 2
1Postgraduate Institute of Science, University of Peradeniya, Sri Lanka
1Department of Geography, University of Peradeniya Sri Lanka
1. Introduction
Moragahakanda - Kaluganga reservoir project is a multipurpose water resources based
development project. Although initial work started in 1994, the project activities accelerated in
2015. It will be completed by the year 2020. The total resettlement families of this development
programme are 2,350. The National Involuntary Resettlement policy of Sri Lanka has
emphasized, when re-settling the affected people due to a development programme, previous
livelihood system, common property resources, and services, should be re-established by the
Government. Accordingly, those who were benefited from tank systems will receive another set
of tanks and its benefits. Under this programme, 9 tanks were newly constructed and 3 were
rehabilitated for the purpose of continuous improvement of living conditions of resettled
community by the year 2018. Although the EIA was approved for constructing new tanks in the
area, it is need to understand the environmental impacts, because if there are future issues, the
project proponent can include mitigating measures. Hence, the objective of this study is to
identify the current usage pattern of these tanks and examine the environmental impacts in
selected aspects such as groundwater table, soil moisture, forest cover, fauna and flora.
2. Methodology
The field survey was commenced at the beginning of March, 2018 and it was completed by the
end of June 2018. Primary and secondary data were collected through questionnaire survey,
interviewing, direct observations and reports. Sieve Analysis, Atterberg limits tests, Moisture
content determination test were carried out to determine the Soil moisture content and to classify
the soil. Three samples (1kg for each sample) were collected from each site at different distance
and the soil properties of each site were compared with the regional soil properties. When
Calculated mass of moisture is (W2 W3) and Calculated mass of dry soil is (W3 W1) the
moisture content of the soil (w%) could be obtained using w (%) = [(W2 W3) * 100] / (W3
W1). Groundwater level of the study area was measured by a graduated steel tape using domestic
wells. Well samples were selected in random manner and the average values of each site were
compared with the previous regional groundwater level. A rapid reconnaissance survey of the
entire study area was conducted initially to identify major vegetation types and their distribution
in the area. Sampling plots for the floral study was ―10 m X 10 m, and used 20 plots under the
purposive sampling method to cover very significant areas including new wetlands. In addition
to that a Zig Zag mode transect survey was used to identify the terrestrial animals in the area.
Seventh UGIT International Conference on “Climate Change, Disaster Risk Reduction, and Sustainable
Development through Geospatial Technologies” (CDSGeo-2018)
50
3. Results and Discussion
3.1 Use of Tanks
The main water sources for these 9 tanks are Kalu-ganga reservoir irrigation water and rain
water. These new tanks provide water for Irrigation water supply, fishing, domestic consumption
and day to day activities. Each tank has 5 ha of command area and some villagers use this water
to cultivate vegetables and some fruits including mango and papaya.
3.2 Groundwater Impact
Before construction of tanks, average ground water level of this region was 8m - 10m in the dry
season. With the construction of tank system, there is sharp increase of the ground water level.
Average ground water level of the study area within 50m distance from the tank is approximately
6 m 7 m in the dry season. This may be due to high ground water recharge due to the tank
system and water table is near to the surface. In the rainy months the groundwater level rises near
to the ground surface. Previous condition and current condition of the ground water level of the
area are shown in Table 01.
Table 01: Ground Water level differences of pre and post tank period
Tank
Average Groundwater level of the
area before construction the tank
(m) (June 2016)
Average Ground Water level of the area after
construction the tank (m)
(June 2018)
Tank 02
8.5
4.9
Tank 04
11
9.5
Tank 06
9
5.7
Tank 10
10.5
7.1
The ground water level of the study area varies with the distance from tank margin. (Figure: 04).
Groundwater level has been gradually decreases with the increase of the distance from the tank.
In the far catchment (600 m far away) groundwater level has been recorded as 10.5 m in the
month of July. This value may be similar to the previous groundwater condition of the area.
However, groundwater level has been reach to the surface level in the rainy season and
approximately 5 m below to the ground level in the dry months of June.
3.3 Soil moisture condition
Soil samples which are collected 600m away from the tanks show narrow range of water holding
capacity, low organic matter content. It represent the past soil moisture condition of the area. Soil
moisture content is very dependent on soil type and the clay content. Also organic matter content
of the soil reduced when distance from the tank increases. High organic matter content presents
in adjacent area of the tank system. It may positively affect the growth and yield of crops in these
areas. The soil moisture condition and the respective distance are shown in Table 02. As shown
in the table Soil moisture condition of the 600 m away from the tank (around 5 %) may be
similar to the previous situation and it has been changed as around 20-30% in the vicinity of
tanks.
Seventh UGIT International Conference on “Climate Change, Disaster Risk Reduction, and Sustainable
Development through Geospatial Technologies” (CDSGeo-2018)
51
Table 02: Soil moisture content variation with the distance from Tank
3.4 Forest cover changes and changes of the floral species in the area
According to the forest classifications of Sri Lanka, there are dry monsoon forest, moist
monsoon forests, scrublands, riverine forests, and grasslands in the area. The undisturbed dry-
mixed evergreen forest species such as Ebony, Weera, Mora, Wewarana, Milla, Welan, Kon,
Madan, Lunumadala, Halmilla, Maila, Thimbiri, Ehela, Daminiya, Kumbuk, Burutha, Palu and
Helamba, have been recorded. The main impacts due to the tank project on these natural forest
cover is fragmentation and loss of tree species covering approximately 115 ha. During the
project some sections change in to human modified habitats such as home gardens, paddy fields,
agricultural lands.
3.5 Changes of the faunal species in the area
Before implement the project these are rich in especially charismatic large mega fauna such as
Elephants , Leopards and Samburs. However, with the expansion of the human interventions,
wild animals like elephant, leopards are not dominant anymore. With the constructions of tank
system, it was introduced livestock animals like cattle and inland fish species were introduced to
the area.
4. Conclusions
These newly established tank systems provide water for domestic purposes and also the
irrigation purposes to increase the livelihood of the resettled people. Ground water level and soil
moisture content are high in the area adjacent to the tanks and it shows positive impact to the
area especially in the dry season. The average groundwater level has been increased from 10-11
m to the 5-6 m towards the ground surface level. Further soil moisture condition has been change
as 20% - 30 % from, around 5% at least in the vicinity of tanks even in the dry season.
Considerable forest cover (115 ha) has been lost to the area and there were not any records of
lost of endemic species in the area. Further, with the arrival of new species related to the wet
environments and agricultural environment, the floral diversity has been increased. Regarding
the faunal species, some of the species including Leopards and Elephants have been migrated in
side to the forest and some of the species like wild boars and hares still visiting the area.
Distance
(m)
Moisture level content (%)
Tank 05
Tank 09
Tank 10
1
30.38
32.12
29.28
10
19.11
19.24
19.09
100
7.24
6.67
6.38
300
6.19
4.54
5.67
600
4.48
4.17
4.98
Seventh UGIT International Conference on “Climate Change, Disaster Risk Reduction, and Sustainable
Development through Geospatial Technologies” (CDSGeo-2018)
52
Accordingly, the emerged environmental changes due to the newly built tank system are not very
much harm to the environment and it has also created some positive impacts.
References
Mahaweli Authority of Sri Lanka, 2015: Environmental Impact Assessment Report -
Modifications to configurations of Moragahakanda-Kaluganga Projects proposed Upper Elehara
Canal (Uec), Canal from Mannakkattiya Tank to Mahakanadarawa Tank and
Kalugangamoragahakanda Link Canal Project, Sri Lanka.
Ministry of Irrigation and Water Resources Management, 2010: Resettlement
Implementation Plan for the Moragahakanda Agricultural Development Project, Sri Lanka,
Colombo.
Samarakoon, S.M.D., J. Gunathilake, K.K.S.A.Withanage, 2016: Residential Land Suitability
Model for resettlement Plan of Environmental Impact Assessment: A case Study-Kaluganga
Development Project, Colombo.
Seventh UGIT International Conference on “Climate Change, Disaster Risk Reduction, and Sustainable
Development through Geospatial Technologies” (CDSGeo-2018)
ResearchGate has not been able to resolve any citations for this publication.
Residential Land Suitability Model for resettlement Plan of Environmental Impact Assessment: A case Study-Kaluganga Development Project
  • S M D Samarakoon
  • J Gunathilake
  • K K S A Withanage
Samarakoon, S.M.D., J. Gunathilake, K.K.S.A.Withanage, 2016: Residential Land Suitability Model for resettlement Plan of Environmental Impact Assessment: A case Study-Kaluganga Development Project, Colombo.
Environmental Impact Assessment Report -Modifications to configurations of Moragahakanda-Kaluganga Projects proposed Upper Elehara Canal (Uec), Canal from Mannakkattiya Tank to Mahakanadarawa Tank and Kalugangamoragahakanda Link Canal Project
  • Mahaweli Authority Of Sri
  • Lanka
Mahaweli Authority of Sri Lanka, 2015: Environmental Impact Assessment Report -Modifications to configurations of Moragahakanda-Kaluganga Projects proposed Upper Elehara Canal (Uec), Canal from Mannakkattiya Tank to Mahakanadarawa Tank and Kalugangamoragahakanda Link Canal Project, Sri Lanka.