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Fernerkundungsbasierte Modellierung und hydrologische Messungen zur Analyse und Bewertung der landwirtschaftlichen Wassernutzung in der Region Khorezm (Usbekistan)
Abstract
Die Bewässerungslandwirtschaft in Mittelasien ist geprägt von schwerwiegenden ökologischen und ökonomischen Problemen. Zur Verbesserung der Situation auf dem hydrologischen Sektor wird daher seitens der mittelasiatischen Interstate Commission for Water Coordination (ICWC) die Einführung des Integrated Water Resource Management (IWRM) gefordert. Wichtige Herausforderungen zur Optimierung der Wassernutzung im Aralsee-Becken sind dabei die Schaffung von Transparenz sowie von Möglichkeiten zur Überwachung der Landnutzung und der Wasserentnahme in den Bewässerungssystemen. Im Detail fokussierte diese Arbeit auf das Bewässerungssystem der Region Khorezm im Unterlauf des Amu Darya südlich des Aralsees. Die Arbeit zielte darauf ab, (1) objektive und konsistente Datengrundlagen zum Monitoring der Landnutzung und des Wasserverbrauchs innerhalb des Bewässerungslandes zu schaffen und (2) auf Basis dieser Ergebnisse die Funktionsweise des Bewässerungssystems zu verstehen sowie die Land- und Wassernutzung der Region zu bewerten. Um diese Ziele zu erreichen, wurden Methoden der Fernerkundung und der Hydrologie miteinander kombiniert. Fernerkundliche Schlüsselgrößen der Arbeit waren die Kartierung der agrarischen Landnutzung und die Modellierung der saisonalen tatsächlichen Evapotranspiration. Es wurde eine Methode vorgestellt, die eine Unterscheidung verschiedener Landnutzungen und Fruchtfolgen der Region durch die temporale Segmentierung von Zeitserien aus 8-tägigen Kompositen von 250 m-Daten des MODIS-Sensors ermöglicht. Durch die mehrfache Anwendung von Recursive Partitioning And Regression Trees auf deskriptive Statistiken von Zeitseriensegmenten konnte eine hohe Stabilität erzielt werden (overall accuracy: 91 %, Kappa-Koeffizient: 0,9). Täglich von MODIS aufgezeichnete Landoberflächentemperaturen (LST) bildeten die Basis zur fernerkundungsbasierten Modellierung der saisonalen tatsächlichen Evapotranspiration (ETact) für die sommerliche Vegetationsperiode. Aufgrund der hohen zeitlichen und groben räumlichen Auflösung der verwendeten MODIS-Daten von 1 km waren leichte Modifikationen des zur Modellierung eingesetzten Surface Energy Balance Algortihm for Land (SEBAL) erforderlich. Zur Modellierung von ETact wurden MODIS-Produkte (LST, Emissionsgrad, Albedo, NDVI und Blattflächenindex) und meteorologische Stationsdaten aus Khorezm verwendet. Die Modellierung des fühlbaren Wärmeflusses, einer Komponente der Energiebilanzgleichung an der Erdoberfläche, erfolgte mittels METRIC (High Resolution and Internalized Calibration), einer Variante des SEBAL. Die Landnutzungsklassifikation fungierte als zentraler Eingangsparameter, um eine automatisierte Auswahl der Ankerpunkte des Models sicherzustellen. Da innerhalb der MODIS-Auflösung aufgrund der Mischpixelproblematik keine homogen feuchten oder trockenen Bedingungen im Bewässerungsgebiet gefunden werden konnten, wurden die Landnutzungsklassifikation, der NDVI und die ASCE-Referenz-Evapotranspiration zur Abschätzung des tatsächlichen Zustands an den Ankerpunkten herangezogen. Weiterhin wurden umfassende Geländemessungen durchgeführt, um in der Vegetationsperiode 2005 die Zu- und Abflussmengen des Wasser von und nach Khorezm zu bestimmen. Die abschließende Bewertung der Land- und Wassernutzung basierte letztendlich auf der Bildung von Wasserbilanzen und der Berechnung anerkannter Performanceindikatoren wie der Ratio aus Drainage und Wasserentnahme oder der depleted fraction. Für die landwirtschaftliche Nutzung im Rayon Khorezm wurde für die Sommersaison 2005 eine Wasserentnahme von 5,38 km3 ermittelt. Damit übertrafen die Messergebnisse die offiziell verfügbaren Daten der ICWC um durchschnittlich 37 %. Auf die landwirtschaftliche Fläche bezogen ergab sich für Khorezm im Jahr 2005 eine mittlere Wasserentnahme von 22.782 m3/ha. In den Subsystemen schwankten diese Werte zwischen 17.000 m3/ha und 30.000 m3/ha. Allerdings konnte an den Systemgrenzen, an denen die Messungen durchgeführt werden, der aus den fernerkundungsbasierten Modellierungen auf WUA-Level erwartete abnehmende Gradient der Wasserentnahme zwischen Oberlauf und Unterlauf nicht nachvollzogen werden. Als Ursache für diese Diskrepanz sind vor allem die Versickerungsverluste im Kanalsystem zu nennen, die den Grundwasserkörper großräumig auffüllen und auf Feldebene nicht zur oberflächlichen Bewässerung zur Verfügung stehen. Monatliche Bilanzierungen und die Analyse der Performanceindikatoren führten zu denselben Ergebnissen. In dieser Arbeit konnte gezeigt werden, dass sich mit Methoden der Fernerkundung objektive und konsistente Daten der agrarischen Landnutzung und des Wasserverbrauchs für ein regionales Monitoring erstellen lassen. Da in den benachbarten Regionen gleiche atmosphärische Bedingungen und ähnliche Anbausorten anzutreffen sind, ist anzunehmen, dass beide Verfahren auch auf der Planungsebene in einem IWRM für die übrigen Mittel- und Unterläufe von Amu Darya und Syr Darya ein hohes Anwendungspotenzial besitzen. The recently founded states of Middle Asia face serious economical and ecological problems in irrigated agriculture. Thus, the introduction of the Integrated Water Resource Management (IWRM) is one of the major aims of the Interstate Commission for Water Coordination (ICWC) of Middle Asia. This study focuses on the irrigation and drainage systems of Khorezm, located in the lower Amu Darya Basin. The scientific gaols were (1) to generate objective and consistent data to measure agricultural land use and water consumption in irrigated areas of the Khorezm region and (2) to analyze the functioning of the irrigation system to assess the use of land and water. Remote sensing in combination with hydrological measurements and irrigation performance indicators were found suitable to achieve these aims. A method was developed to classify agricultural land use for the entire Khorezm region by temporal segmentation of 8-day 250 m MODIS time series. The application of Recursive Partitioning And Regression Tree (RPART) on temporal segments of the time series enabled stable results and portability with 91% overall accuracy and a Kappa coefficient of 0.9. Daily MODIS 1 km Land Surface Temperature (LST) data were used for modeling seasonal actual evapotranspiration (ETact) of the summer vegetation period. The Surface Energy Balance Algorithm for Land (SEBAL) was slightly modified to account for the coarse spatial resolution of MODIS data and for semi-operational purposes. MODIS 1 km land products (LST, emissivity, albedo, NDVI, and leaf area index), and meteorological data were combined for modeling ETact. The sensible heat flux was calculated according to the METRIC (Mapping EvapoTranspiration at High Resolution and Internalized Calibration) variant of SEBAL. Aggregated to MODIS 1 km scale, the land use classification was the determining parameter to select hot and cold anchor points needed to model sensible heat fluxes automatically. The probability to find completely dry or wet conditions within a 1 km grid is very low. Thus, classification results, NDVI, and ASCE-EWRI reference evapotranspiration (ETref) were used to adjust the estimations of the vertical temperature gradient at the best fitting anchor points (similar to METRIC). Furthermore, flow measurements were recorded for 2005 to generate a hydrological data set for balancing. The water balance was achieved by integrating the remotely sensed evapotranspiration. Additionally, widely accepted irrigation performance indicators such as relative evapotranspiration, drainage over inflow ratio, and depleted fraction were calculated on a monthly base to investigate the functioning of the canal network in Khorezm on regional scale. For agricultural use, withdrawals of 5.38 km3 were measured in the vegetation period 2005. The values were on average 37% higher than the official data of the ICWC. Within the system boundaries water amounts of 22,782 m3/ha were available for irrigation. Comparisons between subsystems showed regional disparities of withdrawals ranging from 17,000 m3/ha to 30,000 m3/ha. The upstream-downstream gradient of irrigation water supply expected from the remote sensing modeling results could not be found at the regional water distribution level. In comparison with the remote sensing results it can be summarized that water consumption at the field level (MODIS pixel) or WUA level does not reflect the water intake at the upstream distribution nodes. Monthly water balances and performance indicators highlighted similar results. During the leaching and the main irrigation period in 2005, an increase of soil moisture and groundwater was recorded. The discharge of groundwater followed the irrigation phase in September. However, even in the main irrigation season (July and August), the average drainage over intake ratio is 45% and in the upper part of the irrigation system almost reaches 60%. This concludes a high potential for water saving. Although high discharges in the regional drainage system were found poor drainage systems are reported at the field level. Evidently the main drainage canals of the region work as large scale groundwater collectors rather than fulfill their designated use to collect saline water from the field level. The study proofed the importance to collect reliable and consistent data for hydrological analyses in Middle Asia. For the Khorezm region the presented remote sensing methods indicated their ability to supply data for hydrological monitoring on a regional scale. Remotely sensed crop rotation patterns and water consumption offered the view on field and WUA levels inside the irrigation water distribution administrations. Both methods are portable to regions with similar crops and good climatic conditions, for instance the middle and lower course of the Amu Darya and Syr Darya River.
... • Between 3.5 and 4.0 km³ of water during vegetation period and 1.0 to 1.5 km³ during winter period diverted from the Amudarya (Conrad, 2006); irrigated area in Khorezm is around 275,000 ha ...
... • Canal system length of 16,233 km (Conrad, 2006) reaching from the Amudarya to the borders of Turkmenistan and Karakalpakistan, only 11% of the canals lined (Ibrakhimov, 2004), on local level no discharge measurement structures • Irrigation water pumped or diverted by gravity from canals, applied as furrow irrigation for cotton and some vegetables, basin irrigation for wheat, rice, maize and sorghum Figure 2 shows five trends which are likely to influence this process either by increasing demand or by decreasing supply. The upstream irrigation and energy developments mentioned in the figure highlight the significance of the Amudarya watershed being a trans-boundary management unit. ...
... Instead, a reduction of actual evapotranspiration to 80% to 90% of potential evapotranspiration even in water rich years shows that the water demand of crops is not satisfied. For tail-end locations, Conrad (2006) shows an even less satisfactory situation with actual evapotranspiration reduced to 75% of the potential level in 2005, although gross water withdrawals were high averaging to 2240 mm for the whole Khorezm region in the vegetation period 2005. ...
Khorezm region is located in the northwest of Uzbekistan, approximately 350 km from the current shore of the Aral Sea. It comprises a large-scale irrigation system which conveys water from the river Amudarya to agricultural land cropped mainly with cotton, wheat, and rice. Khorezm's water resources are vulnerable because they depend on upstream developments and are indispensable for rural livelihoods and state budgets. Since water scarcity is expected to increase in the future, sustainable water management is a necessity. Hence the objectives of the paper are to (1) conceptualise the distinctive features of water management in Khorezm, (2) provide an integrated analysis of water management by establishing linkages between society, technical infrastructure, and the bio-physical environment, and (3) make policy and technology recommendations for improved water management. To conceptualise water management in Khorezm, the paper distinguishes three types of practices: formal practices, strategic practices, and discursive practices. Based on these, it presents an analysis of water management on the state water management level, the water user association level, and the farmer and field level. For each level, recommendations are given. The paper concludes that elements of IWRM such as transparency, accountability, participation, and technical efficiency are relevant to improve water management in Khorezm as elsewhere. In addition, it suggests for Khorezm, in particular, to create legal space for agency and innovation. Technical tools such as models acquire additional importance in this context for facilitating transparency and enabling agents across the management hierarchy to access and make use of information. © Springer International Publishing Switzerland 2016. All rights are reserved.
... Length of the collector drainage system (CDS) of the Khorezm oasis and its estimated network density. The total area taken into consideration is 455,200 hectares (Hydromelioration Expedition, OGME Table 6 Pitnakarna main canal of the Figure 1 Overview of the irrigation and drainage system (source: Conrad, 2006 Average monthly values of reference evapotranspiration and precipitation (means from 1985-2007 The Organizational structure of the Map Uzbek word for canals - ...
... As in all irrigation systems located in flat terrain such as is the case in the Khorezm region, a second infrastructural network, the drainage system became necessary to manage groundwater table and control soil salinity. The major branches of the irrigation and drainage system are presented in Fig. 1. Figure 1 Overview of the irrigation and drainage system (source: Conrad, 2006) The long-term annual average reference evapotranspiration (ETo) and precipitation for the last 25 years in the Khorezm region are 1,338 and 94 mm, respectively (Fig. 2). The maximum ETo occurs during the months of June (221 mm) and July (215 mm) whereas average rainfall during June and July is 4 and 1 mm, respectively. ...
... One relevant piece of information indicating the potential water availability is the distance of the canal in a given WCA to the entrance point of the irrigation system it belongs to (Conrad 2006 , Fig. 6). Estimates were completed for several configurations of the irrigation system and on a monthly basis during the vegetation season. ...
Like many irrigation schemes in Central Asia, the one in Khorezm faces a twofold challenge: on the one side, the severe problems inherited from the past need to be remedied and on the other side, the rising supply–demand gap driven by sharpening competition for water and climate change must be dealt with. Located in the lower part of the Amu Darya basin, Khorezm irrigation and drainage scheme is particularly vulnerable to supply–demand gaps. Promising solutions towards adaptation comprise modified strategies of land and water use towards higher efficiency and flexibility in combination with measures to lessen the constraints of the system itself, which was initially designed for the management of a few, large and uniform production units and not for many diverse and small units. Solutions consist of flexible, modeling-based approaches, rearranging institutional settings and establishing economic incentive systems. Flexible modeling allows an integrated use of surface and groundwater resources avoiding or minimizing the impact of water stress on yield. Institutional settings strengthen the position of water users via improved participation and transparency of processes in Water Consumers Associations (WCAs). Economic measures support sustainable resource use strategies and improve the functioning of WCAs. The findings could be extrapolated to other regions of Central Asia with similar conditions and challenges.
... In the water sector, many areas escape central planning and control (Conrad, 2006;Lebel, Garden, & Imamura, 2005). Water theft is a recurring concern in public irrigation systems (Rinaudo, 2002). ...
... New agricultural policies, land reforms, budget constraints, population pressure (leading to fragmentation or expansion of irrigated area within irrigation system) and changing markets have all contributed to the erosion of water control on the ground. The erosion of water control however does not mean less is produced on the land -it can lead to the underreporting of irrigated areas under irrigation (Conrad, 2006;Huppert, 2005;Maruti, 1999;Ul-Haq, 1998). 3 With former colonial States gaining independence and growing dependence on international investments in irrigated agriculture, inappropriate irrigation technology is transferred. ...
... The reported area increased from 37,450 hectares in 1996 to 95,900 hectares one year later, reaching 135,600 hectares in 1998. Conrad (2006) gives the example of underreporting of water utilization in Khorezm Province, Uzbekistan. According to him the water utilized is 37% higher than the official statistics and is mainly used for secondary crops which are produced outside the state order system of cotton and wheat. ...
A political-science perspective of anarchy holds that anarchy is the absence of a ruler. In the water sector, especially in terms of irrigated agriculture, emerging defciencies of public irrigation systems as well as the budget crisis of governments to sustain irrigated agriculture, resulted into increased water user participation. Understanding the apparently increasing smidgeon of anarchy in the water sector includes the appreciation of the complexity of water governance developments such as the introduction of Participatory Irrigation Management (PIM), Irrigation Management Transfer (IMT), basin councils, Integrated Water Resource Management (IWRM) and Multi-Stakeholder Platforms (MSP), as well as the limited role of non-governmental organisations (NGOs) and grassroots organisations (GROs), for decades considered the ‘magic bullet' in taking over and providing state services to the public. We conclude that governance is anarchy by other means.
... • Between 3.5 and 4.0 km³ of water during vegetation period and 1.0 to 1.5 km³ during winter period diverted from the Amudarya (Conrad, 2006); irrigated area in Khorezm is around 275,000 ha ...
... • Canal system length of 16,233 km (Conrad, 2006) reaching from the Amudarya to the borders of Turkmenistan and Karakalpakistan, only 11% of the canals lined (Ibrakhimov, 2004), on local level no discharge measurement structures • Irrigation water pumped or diverted by gravity from canals, applied as furrow irrigation for cotton and some vegetables, basin irrigation for wheat, rice, maize and sorghum Figure 2 shows five trends which are likely to influence this process either by increasing demand or by decreasing supply. The upstream irrigation and energy developments mentioned in the figure highlight the significance of the Amudarya watershed being a trans-boundary management unit. ...
... Instead, a reduction of actual evapotranspiration to 80% to 90% of potential evapotranspiration even in water rich years shows that the water demand of crops is not satisfied. For tail-end locations, Conrad (2006) shows an even less satisfactory situation with actual evapotranspiration reduced to 75% of the potential level in 2005, although gross water withdrawals were high averaging to 2240 mm for the whole Khorezm region in the vegetation period 2005. ...
... A water management tool linking irrigation scheduling approaches and groundwater modelling was developed and applied to optimize current strategies (Awan, 2010). Additionally, Conrad (2006) assessed irrigation performance and established a water balance for the Khorezm region using remote sensing (RS) techniques, geographic information systems and hydrological monitoring. ...
... The available amount exceeds Khorezm's crop requirements by far. Conrad (2006) estimated the actual evapotranspiration of cotton and rice -being the dominant crops in Khorezm -by 830 mm and 880 mm with respect to the vegetation period 2005 using remote sensing techniques. Hydrological monitoring revealed 2,280 mm gross irrigation water input to Khorezm in the same period (Conrad, 2006). ...
... Conrad (2006) estimated the actual evapotranspiration of cotton and rice -being the dominant crops in Khorezm -by 830 mm and 880 mm with respect to the vegetation period 2005 using remote sensing techniques. Hydrological monitoring revealed 2,280 mm gross irrigation water input to Khorezm in the same period (Conrad, 2006). Within Khorezm, the finiteness of water resources becomes apparent mainly in the large differences between the head and the tail end areas of the irrigation system as well as during drought years, such as 2000, 2001 and 2008. ...
The Khorezm region is located in the northwest of Uzbekistan, approximately 350 km from the current shore of the Aral Sea. It comprises a large-scale irrigation system that conveys water from the river Amu Darya to agricultural land cropped mainly with cotton, wheat, and rice. Khorezm's water resources are vulnerable as they depend on upstream developments and are indispensable to rural livelihoods and state budgets. Since water scarcity is expected to increase in the future, sustainable water management is a necessity. Hence, the objectives of the paper are to: (1) conceptualize the distinctive features of water management in Khorezm; (2) provide an integrated analysis of water management by establishing linkages between society, technical infrastructure, and the bio-physical environment; and (3) make policy and technology recommendations for improved water management. To conceptualize water management in Khorezm, the paper distinguishes three types of practices: formal practices, strategic practices, and discursive practices. Based on these, it presents an analysis of water management on the state water management level, the water user association level, and the farmer and field level. For each level, recommendations are given. The paper concludes that elements of integrated water resources management (IWRM) such as transparency, accountability, participation, and technical efficiency are relevant to improve water management in Khorezm, as elsewhere. In addition, it underlines the need to create legal space for agency and innovation. Technical tools such as models are increasingly important for facilitating transparency and enabling agents to access and make use of information across the management hierarchy.
... Müller [8] analyzed the intra-regional crop water allocation in the study region Khorezm and concluded that tail end users constantly have to cope with increased water losses and, in turn, lower water availability, compared to head end users and areas close to the water source. Conrad's [9] findings also indicated high water losses in water conveyance to off-stream districts, which in turn decreased water availability at field level for tail end users. However, linkages between water availability and agricultural output value in Central Asia have as yet received little attention. ...
... About 40% of the precipitation falls in spring, 20-25% in the fall, and only 10% during the summer months. Precipitation has little influence on the growth and development of agricultural crops [9]. ...
... Water availability in each district was estimated stepwise. In a first step, the distances between the border of the WUAs and water intake (source) point of the primary canal that attached each WUA, were calculated using ArcView software following Conrad [9]. Next, the average distance of WUAs from the water intake point was calculated for each of the ten administrative districts (Figure 7). ...
Since irrigation water is assumedly the predominant factor determining crop yield, the difference in irrigation water availability across the administrative sub-districts of the Khorezm region, Central Asia, also inflicts an unequal distribution of agricultural revenues. Considering the national aim of a fair distribution and efficient use of resources, here we analyze the relationships between irrigation water access and rural welfare from 2000 to 2007 by descriptive statistics. Analyses revealed not only the general dependency of agricultural revenue on irrigation water availability, but also occurrence of low land productivity during water scarce years and, irrespective of the annual water availability, in some tail end regions each year. Furthermore, apart from irrigation water availability, land productivity was also impacted by soil quality, cropping structure, and type of land ownership. Fair distribution of water and land resources should also take into consideration population density. It is argued that an anticipated equal and efficient water allocation necessitates improved irrigation water conveyance, distribution, and application efficiency via best water management practices. Liberalization of markets, development of a market infrastructure and improvement in yields also contribute to increased land and water productivity.
... In Khorezm, 230,000 out of 670,000 ha land are annually irrigated for the production of mainly cotton, wheat, and rice (Fritsch et al. 2014). Reportedly, Khorezm extracts annually between 3.5 and 5 km 3 river water of which ca. 95 % is used for agricultural purposes (Conrad 2006). Irrigation water is supplied through huge irrigation systems characterized by open, non-lined canals. ...
... Given an annual freshwater supply to the irrigation system in Khorezm of ca. 3.5-5 km 3 (Conrad 2006), a volume surplus of *0.03 km 3 found in 2002, a year of regular water supply to the region, seems quite modest. It also indicates that the total volume to be stored in the small lakes cannot compete with those offered by the vast water reservoir constructions along the rivers (Rakhmatullaev et al. 2010). ...
In the inner Aral Sea Basin of Central Asia, numerous small lakes scattered over the irrigated landscape supply diverse ecosystem services for humans and nature. This study aimed to estimate the water volumes and assess the potentials of these small lakes for instance as irrigation reserve during the ever-recurring periods of water scarcity in the ecologically endangered Amudarya Delta. Bathymetric measurements gathered in the Khorezm region, Northwest Uzbekistan, permitted developing a statistical relationship between the surface and volume of the lakes. Landsat satellite data enabled for classifying the water bodies and hence deriving lake volumes over the study area. In 2002, the lakes stored ~0.032 km3 water during the winter season, but ~0.057 km3 during the main, 5–6 months spanning irrigation period. The area-wide increase in lake volumes during the irrigation period underlined the magnitude to which the currently practiced, inefficient use of irrigation water, produces excess water that in turn contributes to the existence of the small, mesotrophic lakes. Based on crop water requirements, calculations showed that the reuse of lake water may compensate for water-scarce situations, albeit to a certain extend only. An increased share (13 % above average) of water-intensive rice fields in the vicinity of the lakes substantiated that some lakes are already used in this way. It is argued that, in case of sufficient water quality, as indicated by other studies, more targeted exploration of such lake water can help simultaneously both, increasing food and water security of the households surrounding the lakes and safeguarding a supply to maintain different ecosystem functions. Integrated management of all water resources may reduce excess irrigation water supply to the region, which in turn may lessen the dependency of Central Asian downstream countries on transboundary water and supply water resources for the ecosystems in the river deltas.
... Especially the lack of reliable official data was problematic. Many researchers in Uzbekistan have reported to receive conflicting data sets as well as the suspicion of 'doctored' data (Mueller, 2006;Conrad, 2006;Wegerich, 2005). I am especially aware of examples of economic data and water discharge data, but this is probably connected to the sphere in which our project is active. ...
... But at least of this data I could be pretty sure that it was not doctored to show lower water use or more equal patterns of water use between districts. Such doctoring was sometimes expected on basis of other research results, especially Conrad (2006) and Wegerich (2005). ...
... The cold pixels should have a good vegetation cover, i.e. a high Leaf Area Index (LAI), and a low surface temperature (T S ) and were therefore chosen from cool, well-vegetated land surfaces. Evapotranspiration is assumed to have a cooling effect on surface temperatures (Conrad, 2006). The total available energy at these points, excluding the energy of soil heat flux, was used for evapotranspiration. ...
... The stability of the atmospheric stratification will, however, still have a considerable influence on the sensible heat flux. The vertical air mass exchange will decrease, remain unchanged, or increase depending on whether the air stratification is stable, neutral, or unstable (Conrad, 2006), which is why the aerodynamic heat transfer resistance (r ah ) still needs to be calculated. The aerodynamic heat transfer resistance is affected by the surface roughness (vegetation height, vegetation structure), the wind speeds, and the atmospheric stability, etc. (Li et al., 2009). ...
The actual evapotranspiration is an important, but difficult to determine, element in the water balance of lakes and their catchment areas. Reliable data on evapotranspiration are not available for most lake basins for which paleoclimate reconstructions and modeling have been performed, particularly those in remote parts of Africa. We have used thermal infrared multispectral data for 14 ASTER scenes from the TERRA satellite to estimate the actual evapotranspiration in the 12,800 km(2) catchment of the Suguta Valley, northern Kenya Rift Evidence from sediments and paleo-shorelines indicates that, during the African Humid Period (AHP, 14.8 to 5.5 kyrs BP), this valley contained a large lake, 280 m deep and covering similar to 2200 km(2), which has now virtually disappeared. Evapotranspiration estimates for the Suguta Basin were generated using the Surface Energy Balance Algorithm for Land (SEBAL). Climate data required for the model were extracted from a high-resolution gridded dataset obtained from the Climatic Research Unit (East Anglia, UK). Results suggest significant spatial variations in evapotranspiration within the catchment area (ranging from 450 mm/yr in the basin to the north to 2000 mm/yr in more elevated areas) and precipitation that was similar to 20% higher during the AHP than in recent times. These results are in agreement with other estimates of paleo-precipitation in East Africa. The extreme response of the lake system (similar to 280 m greater water depth than today, and a lake surface area of 2200 km(2)) to only moderately higher precipitation illustrates the possible sensitivity of this area to future climate change. (C) 2012 Published by Elsevier B.V.
... To consider the all signicant inner year characteristics of the dierent crops, the time series are divided into temporal segments. 4 Therefore, all time series, including red, nir, blue, mir, ndvi, evi and temperature, were divided up to ve temporal segments like Conrad 4 suggested and which extract well the inner year variation represented by the 23 time steps. To extract stable and robust parameters, statistic features of the MODIS timeseries as well as on the temporal segments were calculated, which are less sensitive to climatic variations or noise. ...
... 14{16 Therefore, this method is an adequate algorithm to classify land use with time series, leading to a large number of temporal features. 4 In every splitting node of a classication tree an impurity function is minimized to nd the optimal splitting criteria. For the determination of the node impurity and the splitting values of the predictor variables, the Gini index was applied. ...
Remote sensing offers the opportunity to produce land cover classifications for large and remote areas on a yearly basis and is an important tool in regions that lack these information. However often training and validation data to generate annual land cover maps are not available in necessary quantity - being from one year only or covering only a small extent of the region of interest. This study was focused on land use classifications at regional scale with a special emphasize on annual updates under the constraint of limited sampling data. Often, sampling is reduced to one year or to an unrepresentative area extend within the region of interest. The investigations for the period between 2004 and 2009 were conducted in the irrigation systems of the Amu Darya Delta in Central Asia, where reliable information on crop rotations is required for sustainable land and water management. Annual training and validation data were extracted from high resolution land use classifications. For classification, statistical features based on MODIS time series of vegetation indices, reflectance and land surface temperature (LST) were calculated and a random forest algorithm was applied. By a combination of training data from different years, the accuracy could be enhanced from an overall accuracy of 70% to more than 90% for a focused subregion and also good consistency with high resolution images for the other parts of the delta, which has to be confirmed using quantitative validation. A combination of a different number of years was tested. Already two years can be sufficient to generate a robust and transferable random forest to produce yearly land use maps. The study shows the possibility to combine training data from different years for the annual classification of irrigated croplands on a regional scale.
... In the Amu Darya River Delta, about 1,200 mm surface water is used seasonally for cotton production alone (Conrad 2006). Out of this amount, 430 mm is used for pre-season soil leaching (Djanibekov 2008), which is essential in many parts of CA to cope with salinity, and eventually feeds into the groundwater (Ibrakhimov et al. 2007). ...
... This is particularly evident in Central Asia if one looks at basin transfers from the Amu Darya to smaller rivers ). Also, it seems that the Soviet Union created a web of interconnected main canals within irrigation systems (on the Khorezm region in Uzbekistan, see Conrad, 2006;. So far, the interconnectedness of sub-catchments and irrigation systems in formal engineered systems, especially in the former Soviet Union, has not been the focus of research. ...
Examining the water, development and security linkages in Central Asia can feel a bit like solving a Rubik's cube. The Rubik's cube starts to usually find structure and the different pieces find their places when its solver adopts a systematic approach. Still, solving the whole cube takes time and perseverance. This is also the case with water and security in Central Asia as demonstrated by the chapters in this book. In the case of water and security in Central Asia, there are many "faces", including not only the Central Asian states but also the neighbouring countries and other players of global geopolitics; "stickers" such as policies, practices, causes, and impacts; and "colours" such as the different stakeholders, ranging from the micro and meso levels to the macro level. Understanding all these, or getting clarity on the nexus, can seem extremely challenging. Even though none of the chapters alone answers the question of what constitutes water and security in Central Asia, each of them gives thoughtful ideas and information on the complexity of the issue. This book was published as a special issue of the International Journal of Water Resources Development.
... This indicates that approximately 35% of the total water received was lost during conveyance and application. Irrigation efficiency is higher than presented previously by Conrad (2006) and amounts to 48% if the entire vegetation period is considered. The discrepancy between the present and previous findings is likely due to the difference in the spatial and temporal resolution used in the different studies. ...
A decline in water availability due to rising temperatures and growing water demand presents significant and unique challenges to agricultural producers in Uzbekistan. This study investigates the impact of climate change on farm revenues and water use efficiencies in Western Uzbekistan. A spatially explicit stochastic optimization model is used to analyze crop and water allocation decisions under conditions of uncertainty for irrigation water availability in the area for the first time.
Results show farmers’ income could fall by as much as 25% with a 3.2 °C temperature increase and a 15% decline in irrigation. Farmers located in the tail end of the irrigation system could lose an even greater share of their revenues. A more conservative increase in temperature could increase farmer income by as much as 46% with a 2.2° temperature increase and only 8% decline in irrigation water since some crops benefit from extended vegetation periods. Under both pessimistic and optimistic scenarios, environmental challenges due to shallow groundwater tables may improve associated with enhanced water use efficiency.
... In the field of water, the 'dark side' refers to what happens outside the control, or purview, of the formal governance arrangement. Contrary to 'common knowledge' in the water sector on large scale irrigation and the bulk of its governance literature, many areas still escape central planning and control ( Lebel et al. 2005, Conrad 2006, Warner 2012), still lacking the 'soft' coordination of collaborative networks. This may bring violence and lawlessness, but-as we shall argue-also more constructive, productive forms of self-organisation. ...
... The ratio of second crops to winter wheat area for selected WUAs located in Andijan and Ferghana provinces are provided in Figures 5 and 6, respectively. These figures include the state limit for second-crop sowing (Dukhovny et al., 2012 ) and the volume of irrigation water received by the provinces (CAWater-Info, 2012) during the vegetation period (April-September). The state limit for second crops is set in the beginning of the vegetation season. ...
After independence in 1991, Uzbekistan introduced a policy on food security and consequently reduced the irrigated area allocated to cotton and increased the area of winter wheat. Shifting to winter wheat allowed farmers to grow a second crop outside the state-order system. The second crops are the most profitable and therefore farmers tried to maximize the area grown to this second crop. Although the second crops are the most profitable, only few studies have focused on this topic. Evidence is presented which shows that state control of crops has been extended from the main crops, cotton and wheat, to the second crops. Satellite images used for classification of main crops in two provinces of the Ferghana Valley for 2006–2011, highlight that the area utilized for second crops is dependent on the infrastructure that enables access to the water resource, not on the area's position within the irrigation system.
... Some studies have focused on the background to the shift on the national level (Yalcin & Mollinga, 2007) and on the implementation of the shift on the province and district levels (Conrad, 2006, Wegerich, 2009 and the WUA level (Veldwisch, 2007) in Khorezm Province in the lower Amu Darya Basin. While this literature might suggest that there has been a streamlined process of defining hydrological/hydrographic boundaries across Uzbekistan, recent observations in other provinces have highlighted that this is not the case (see also Yakubov, 2012, regarding different approaches to WUAs in Uzbekistan). ...
In the literature on the implementation of national policies there is an assumption that these get implemented uniformly within one country. Here, with a focus on the implementation of national policy on shifting from administrative to hydrological/hydrographic principles of water management in the Zerafshan Valley and the Ferghana Valley in Uzbekistan, this assumption is questioned. The case study demonstrates that national policies are resisted by lower-level bureaucrats, leading to diverse, even contradictory, outcomes of the same policy. The vested interests of a multiplicity of bureaucracies, the power of individual bureaucrats, and the discretional power given to bureaucracies in interpreting national policy are responsible for the different outcomes. The article calls for more comparative assessments across different regions for a better understanding of policy implementation.
... This is particularly evident in Central Asia if one looks at basin transfers from the Amu Darya to smaller rivers (Wegerich, 2011). Also, it seems that the Soviet Union created a web of interconnected main canals within irrigation systems (on the Khorezm region in Uzbekistan, see Conrad, 2006;Wegerich, 2009). So far, the interconnectedness of sub-catchments and irrigation systems in formal engineered systems, especially in the former Soviet Union, has not been the focus of research. ...
The management of water resources according to hydrological boundaries at different implementation levels (river basin, irrigation system, or water user association) is promoted internationally. This approach to water management, especially for the basin, is starting to be challenged from different perspectives: representation within basins, appropriateness for basins in the south, and the challenges of merging boundaries for surface and groundwater sources. It has been challenged only recently in relation to its appropriateness for indigenously constructed (informal) irrigation systems. To these critiques, this paper adds the historical development and originally intended purpose of engineered irrigation systems and therefore calls into question whether it is always possible to introduce hydrological boundary management in the formal systems in Central Asia.
... This is particularly evident in Central Asia if one looks at basin transfers from the Amu Darya to smaller rivers (Wegerich, 2011). Also, it seems that the Soviet Union created a web of interconnected main canals within irrigation systems (on the Khorezm region in Uzbekistan, see Conrad, 2006;Wegerich, 2009). So far, the interconnectedness of sub-catchments and irrigation systems in formal engineered systems, especially in the former Soviet Union, has not been the focus of research. ...
The management of water resources according to hydrological boundaries at different implementation levels (river basin, irrigation system, or water user association) is promoted internationally. This approach to water management, especially for the basin, is starting to be challenged from different perspectives: representation within basins, appropriateness for basins in the south, and the challenges of merging boundaries for surface and groundwater sources. It has been challenged only recently in relation to its appropriateness for indigenously constructed (informal) irrigation systems. To these critiques, this paper adds the historical development and originally intended purpose of engineered irrigation systems and therefore calls into question whether it is always possible to introduce hydrological boundary management in the formal systems in Central Asia.
... The national food self-sufficiency strategy in Uzbekistan, which reallocated irrigated areas from cotton to wheat production, could have led to water savings (Abdullaev et al., 2009;Spoor and Krutov, 2003). However, Conrad (2006) and Wegerich (2009) emphasise the expansion of a second crop after winter wheat in Uzbekistan. ...
While best practice in water management typically calls for the use of a basin-level approach, specific guidance in the absence of basin-level management is fairly scant. This paper reviews the experience of the Syr Darya basin to identify insights related to second best practices for water management at scales below the basin level. This paper first presents the causes for the disintegration of river basin management within the Syr Darya, which include both changes in operation of the Toktogul reservoir and rising water demands due to shifts in agricultural production and land ownership. Focus is then devoted specifically to small transboundary tributaries, where bottom-up cooperation has continued or reemerged in recent times. This paper concludes by highlighting the limitations to singular focus on sub-basins and tributaries, suggesting a balance between more intense cooperation and water control on tributaries and a loose overarching framework at the basin level.
... Annual and seasonal fluctuations in water supply have increased in recent years and, in turn, increasing the risks of receiving insufficient irrigation water (Müller 2006). On average, efficiency of the irrigation system is estimated at 55%, meaning that 45% of the water taken from the river is lost in transport due to infiltration and evapotranspiration (Conrad 2006); field-level studies have indicated an even lower water use efficiency in the region (Tischbein et al 2012). The low irrigation efficiency and notorious oversupply of irrigation water has resulted in shallow groundwater tables and severe waterlogging of soils, resulting in secondary soil salinization in most parts of the region (Ibrakhimov 2007). ...
This article describes various opportunities but also constraints to greater crop diversification, and the impact on local sustainability in the Khorezm province of Uzbekistan in the Aral Sea basin. At present, approximately 70% of the area in this study region is sown to irrigated cotton and winter wheat under the so-called state mandate. We present evidence of the benefits of moving away from this approach toward more diversified farming with an increasing area of alternative crops in the selected region. We report on a series of studies that included a) crop suitability screening based on secondary data, b) joint farmer experiments, and c) a mathematical simulation model with the overarching objective to assess potential benefits and constraints for crop diversification. The findings of this long-term, multiyear, and multidisciplinary approach show that greater crop diversity can increase water use efficiency, and secure farm income in dryland areas prone to water scarcity and soil salinity. In addition, the findings of the simulation model confirmed that crop diversification could secure income of downstream farmers during the climate-driven decline in water availability. Overall, the findings indicate that greater crop diversity and improved access to markets can lead to a sustainable development path in the region.
Full paper: http://www.tandfonline.com/eprint/bR2qnGg7ibGPKDA8D5aD/full
... Furthermore, unofficial data indicate that Uzbekistan utilizes more water than the limits set by the 1987 protocol (Wegerich 2005). Similarly, Conrad (2006) shows for Khorezm Province in Uzbekistan that the water amount extracted from the Amu Darya exceeds official claims. Maybe, since all of the riparian states seem to have increased their water demand without officially admitting it, one riparian state does not want to blame the other riparian state officially. ...
This article explores the cooperation after independence on four Central Asian transboundary rivers. The paper shows that, even though the Central Asian states agreed in 1992 to continue with the basic water-sharing principles, new agreements had to be made. New agreements were only made in basins with large-scale water-control infrastructure, which have transboundary significance or are transboundary themselves. The inequitable water allocation between the riparian states has continued and has not triggered new agreements.
... The flat response curves can possibly be attributed to supplemental N contribution from the groundwater stemming from an upward flux of groundwater leading to nitrate accumulation in the rooting zone, which most likely influenced the soil-N balance and plant-N uptake. For regions with particularly shallow groundwater during the vegetation season such as the Khorezm region (see Forkutsa, 2006), a significant amount of crop water is supplied via upward flow of groundwater (Conrad, 2006;Forkutsa, 2006), which supplement irrigation inputs (Ayars et al., 2006). Most of the N is thus likely to have come from N applied to neighboring fields. ...
Cotton and winter wheat play a vital role in Uzbek agriculture: the first crop is a vital component of the national export revenues, while the latter is key in achieving independence from grain imports. Due to these strategic roles in the national economy, both crops are part of the state procurement system and, hence, are subject to strict regulations imposed to ensure budget revenues and self-sufficiency. However, many factors cause the divergence of crop yields from their technically maximum levels. We analyzed those factors, which hamper achieving the optimum response to fertilizer applications. In a stepwise procedure, we (i) reviewed the technical and financial optimum yield responses of cotton and winter wheat production to fertilizer applications and (ii) analyzed the changes of fertilizer-to-product price ratios to shed light on the agronomic and economic performance of cotton and wheat in the post-Soviet agricultural system of Uzbekistan. The analysis combined data from long-term, historical yield and fertilizer responses, agronomic N-fertilizer response experiments, and socio-economic farm surveys. Quadratic yield-response functions were used to derive economic and technical optimum rates of N-fertilizer applications. Based on the parameterized function and fertilizer-to-product price ratios observed for 1996-2003, we analyzed the difference between recommended fertilization and economic optimum application rates. Results showed that under the state procurement system, Uzbek farmers may not necessarily tend to maximize the profits from their cotton and wheat production. The level of subsidies and the differential crop support by the state induce farmers to follow the official fertilizer recommendations to ensure that they fulfill the production targets even if it implies higher production costs. The present gaps between the officially recorded yields and those technically achievable given the agro-ecological conditions in Uzbekistan cannot be narrowed by only improving N-fertilizer management. It would require additional efforts to improve cotton and wheat yields.
... Adapting to demands Khorezm, although it lies in the lower reaches of the Amu Darya basin, has always experienced a general situation of water abundance (Conrad, 2006;Veldwisch, 2008a;Veldwisch, 2010;Oberkircher, forthcoming). The relatively high availability of water reduces conflicts over this resource. ...
On the basis of intensive fieldwork in the period 2002–2006, which combined interviews with direct observations, the implementation
of two policies in the field of agricultural water management in Uzbekistan is analysed: the reform of the water bureaucracy
along basin boundaries and the establishment of Water Users Associations. It is shown that the Uzbek government used these
policies creatively for addressing some pressing issues, while the inherent decentralisation objective was pushed to the far
background. Both reforms are used to strengthen the state’s grip on agricultural production regulation. The latter is at the
centre of day-to-day agricultural water management dynamics. It is shown that decentralisation policies originally developed
in society-centric policy processes cannot be easily applied in countries with state-centric politics such as Uzbekistan.
KeywordsIrrigation-Water Users Associations-Water reform-Agrarian change-State-centric politics
... The enormous water movement to the storage in July and August, when water supply is at highest level, shows however, the variability of this delay in Shomokhulum. The WUA is located in the very flat south-west of Khorezm, where drainage problems at regional level occur (Conrad 2006). Obviously the drainage is unable to remove the water which was excessively supplied during both months, when intakes where much higher than demand (Table 2). ...
Irrigation water management in Central Asia is notorious for its inefficiency. We assessed the operational performance of
the irrigation scheme in one Water Users Association (WUA), Shomakhulum, in Khorezm district, Uzbekistan, in 2007 to provide
recommendations for strategic water management planning. Relative evapotranspiration (RET), delivery performance ratio (DPR),
drainage ratio (DR), depleted fraction (DF), overall consumed ratio (OCR), field application ratio (FAR) and conveyance ratio
(CR) were used as performance indicators. The components of the water balance were obtained through remote sensing techniques
and hydrological field measurements. The surface energy balance algorithm for land (SEBAL) was applied to MODIS satellite
data to derive actual and potential evapotranspiration. Inflows and outflows were quantified with field measurements in the
irrigation and drainage network using discharge rating curves. Ponding experiments allowed determining canal seepage losses.
Water balances at field level were established for application efficiency estimations. The indicator values were then compared
to efficiency target values taken from the literature in order to assess the operational capabilities of the irrigation scheme.
The general performance of the irrigation scheme is very poor. DPRs exceeding 1.0 indicate that more water is delivered to
the system than is demanded. The seasonal DF of 0.4 is lower than the target value of 0.6. Losses during the field application
averaged at 57%, which is 24% above target values. Seasonal DR, OCR, CR and RET are 0.55, 0.51, 0.76 and 0.82 against the
target values of 0.1, 0.54, 0.84 and 0.75, respectively. We conclude that the distribution mechanism can be considerably improved.
Besides improving water distribution (timing and equity) in the network, another recommended intervention would be to increase
the DF, particularly by interventions at field level that raise the FAR, which in turn will improve DR and OCR. This can be
achieved by introducing modern water management approaches such as laser leveling, double-sided irrigation, and control of
inflow through flow-measuring devices installed at farm gates, and adequate water pricing.
KeywordsIrrigation performance indicators–SEBAL–Central Asia–Drainage
... The enormous water movement to the storage in July and August, when water supply is at highest level, shows however, the variability of this delay in Shomokhulum. The WUA is located in the very flat south-west of Khorezm, where drainage problems at regional level occur (Conrad 2006). Obviously the drainage is unable to remove the water which was excessively supplied during both months, when intakes where much higher than demand (Table 2). ...
This book offers the first multidisciplinary overview of water resources issues and management in the Aral Sea Basin, covering both the Amu Darya and Syr Darya River Basins. The two main rivers of Amu Darya and Syr Darya and their tributaries comprise the Aral Sea Basin area and are the lifeline for about 70 million inhabitants in Central Asia. Written by regional and international experts, this book critically examines the current state, trends and future of water resources management and development in this major part of the Central Asia region. It brings together insights on the history of water management in the region, surface and groundwater assessment, issues of transboundary water management and environmental degradation and restoration, and an overview of the importance of water for the key economic sectors and overall socioeconomic development of Central Asian countries, as well as of hydro politics in the region. The book also focusses on the future of water sector development in the Basin, including a review of local and international actors, as well as an analysis of the current status and progress towards the Sustainable Development Goals by Basin countries. The book will be essential reading for those interested in sea basin management, environmental policy in Central Asia and water resource management more widely. It will also act as a reference source for decision-makers in state agencies, as well as a background source of information for NGOs. Large river basins are dynamic and complex entities. Defined by hydrological boundaries, they are nearly always shared by more than one country. Encompassing a diverse range of landscapes with often huge temporal and spatial variability of resources, they are put to different and often conflicting uses, and managed by a range of institutions and organisations. While an intrinsic part of Nature, many have been extensively engineered and used by people, often with adverse consequences. Each major river basin has its own development trajectory and often fascinating history. Bringing together multidisciplinary teams of experts, this series explores these complex issues, identifies knowledge gaps and examines potential development pathways towards greater sustainability.
This study reports cotton production in five Central Asian countries (Uzbekistan, Turkmenistan, Tajikistan, Kazakhstan, and Kyrgyzstan), where cotton is grown on highly fertile soils irrigated from Amu Darya, Syr Darya and tributaries since 500–600 A.D. However, wide scale cotton production began only after the capture of the area by Czars in the second half the nineteenth century. Average water use efficiency from the Central Asian rivers is poor (~55%) due to huge water losses from head to tail end. All countries in the region are not densely populated; however, the most organized cotton production is carried out in Uzbekistan that is second largest cotton exporter in the world. Cotton production is supported by the scientific research carried out at the Uzbek Scientific Research Institute of Cotton Breeding and Seed Production. The institute has developed a large number of new cotton cultivars and introduced novelties in irrigation techniques and market economy. Organic cotton is grown in Sughd area of Tajikistan and Kyrgyzstan. Compared to Uzbekistan, cotton production is carried out on a smaller scale in the other Central Asia states. Better administration and technical support, improved state policies toward the uplift of farmers with creation of balance in inputs and outputs would create a viable infrastructure to ensure long term improvements in economic, ecological, and social sectors.
Like many irrigation schemes in Central Asia, the one in Khorezm faces a twofold challenge: on the one side, the severe problems inherited from the past need to be remedied and on the other side, the rising supply–demand gap driven by sharpening competition for water and climate change must be dealt with. Located in the lower part of the Amu Darya basin, Khorezm irrigation and drainage scheme is particularly vulnerable to supply–demand gaps. Promising solutions towards adaptation comprise modified strategies of land and water use towards higher efficiency and flexibility in combination with measures to lessen the constraints of the system itself, which was initially designed for the management of a few, large and uniform production units and not for many diverse and small units. Solutions consist of flexible, modeling-based approaches, rearranging institutional settings and establishing economic incentive systems. Flexible modeling allows an integrated use of surface and groundwater resources avoiding or minimizing the impact of water stress on yield. Institutional settings strengthen the position of water users via improved participation and transparency of processes in Water Consumers Associations (WCAs). Economic measures support sustainable resource use strategies and improve the functioning of WCAs. The findings could be extrapolated to other regions of Central Asia with similar conditions and challenges.
Like many irrigation schemes in Central Asia, the one in Khorezm faces a two-fold challenge: on the one side, the severe problems inherited from the past need to be remedied and on the other side, the rising supply-demand gap driven by sharpening competition for water and climate change must be dealt with. Located in the lower part of the Amu Darya basin, Khorezm irrigation and drainage scheme is particularly vulnerable to supply-demand gaps. Promising solutions towards adaptation comprise modified strategies of land and water use towards higher efficiency and flexibility in combination with measures to lessen the constraints of the system itself, which was initially designed for the management of a few, large and uniform production units and not for many diverse and small units. Solutions consist of flexible, modeling-based approaches, re-arranging institutional settings and establishing economic incentive systems. Flexible modeling allows an integrated use of surface and groundwater resources avoiding or minimizing the impact of water stress on yield. Institutional settings strengthen the position of water users via improved participation and transparency of processes in Water Consumers Associations (WCAs). Economic measures support sustainable resource use strategies and improve the functioning of WCAs. The findings could be extrapolated to other regions of Central Asia with similar conditions and challenges.
Like many irrigation schemes in Central Asia, the one in Khorezm faces a twofold challenge: on the one side, the severe problems inherited from the past need to be remedied and on the other side, the rising supply–demand gap driven by sharpening competition for water and climate change must be dealt with. Located in the lower part of the Amu Darya basin, Khorezm irrigation and drainage scheme is particularly vulnerable to supply–demand gaps. Promising solutions towards adaptation comprise modified strategies of land and water use towards higher efficiency and flexibility in combination with measures to lessen the constraints of the system itself, which was initially designed for the management of a few, large and uniform production units and not for many diverse and small units. Solutions consist of flexible, modeling-based approaches, rearranging institutional settings and establishing economic incentive systems. Flexible modeling allows an integrated use of surface and groundwater resources avoiding or minimizing the impact of water stress on yield. Institutional settings strengthen the position of water users via improved participation and transparency of processes in Water Consumers Associations (WCAs). Economic measures support sustainable resource use strategies and improve the functioning of WCAs. The findings could be extrapolated to other regions of Central Asia with similar conditions and challenges.
Accurate quantification of the rate of groundwater (GW) recharge, a pre-requisite for the sustainable management of GW resources, needs to capture complex processes, such as the upward flow of water under shallow GW conditions, which are often disregarded when estimating recharge at a larger scale. This paper provides (1) a method to determine GW recharge at the field level, (2) a consequent procedure for up-scaling these findings from field to irrigation scheme level and (3) an assessment of the impacts of improved irrigation efficiency on the rate of GW recharge. The study is based on field data from the 2007 growing season in a Water Users Association (WUA Shomakhulum) in Khorezm district of Uzbekistan, Central Asia, an arid region that is characterized by a predominance of cotton, wheat and rice under irrigation. Previous qualitative studies in the region reported irrigation water supplies far above the crop water requirements, which cause GW recharge. A field water balance model was adapted to the local irrigation scheme; recharge was considered to be a fraction of the irrigation water losses, determined as the difference between net and gross irrigation requirements. Capillary rise contribution from shallow GW levels was determined with the HYDRUS-1D model. Six hydrological response units (HRUs) were created based on GW levels and soil texture using GIS and remote sensing techniques. Recharge calculated at the field level was up-scaled first to these HRUs and then to the whole WUA. To quantify the impact of improved irrigation efficiency on recharge rates, four improved irrigation efficiency scenarios were developed. The area under cotton had the second highest recharge (895 mm) in the peak irrigation period, after rice with 2,514 mm. But with a low area share of rice in the WUA of <1 %, rice impacted the total recharge only marginally. Due to the higher recharge rates of cotton, which is grown on about 40 % of the cropped area, HRUs with a higher share of cotton showed higher recharge (9.6 mm day−1 during August) than those with a lower share of cotton (4.4 mm day−1). The high recharge rates in the cotton fields were caused by its water requirements and the special treatment given to this crop by water management planners due to its strategic importance in the country. The scenario simulations showed that seasonal recharge under improved irrigation efficiency could potentially be reduced from 4 mm day−1 (business-as-usual scenario) to 1.4 mm day−1 (scenario with maximum achievable efficiency). The combination of field-level modeling/monitoring and GIS approaches improved recharge estimates because spatial variability was accounted for, which can assist water managers to assess the impact of improved irrigation efficiencies on groundwater recharge. This impact assessment enables managers to identify options for a recharge policy, which is an important component of integrated management of surface and groundwater resources.
This study presents a method for detecting changes in land and soil cover of the southern Aralkum using high-temporal-resolution time series satellite data. The results demonstrate that the MODIS time series classification is a valuable tool to produce accurate landscape classification, landscape change maps and statistics for large areas as the Aralkum. A significant proportion of the emerged soil remained devoid of dense vegetation and became a salt desert. Only a small part of the salt desert in the study area, near the former Amu Darya’s mouth, was converted to shrubland and reeds between 2000 and 2008. Monitoring land cover condition and analysing land cover change in the Aralkum is of great importance, since the ecological situation is still very dynamic and large parts of the landscape in the Aralkum are unstable.
Irrigated agriculture is widespread in the Central Asian drylands and important for food security of the region. However irrigation practices based on rules made for cotton production on large units do not provide adequate guidance for the now widespread small farms that produce cotton wheat and rice. Excessive unsustainable water use is the consequence. Land and water resource management practices were analysed in 2006 for the irrigated area (approx. 1885 ha) of a water users' association (WUA) as a case study. The Shomakhulum WUA is situated in the Khorezm region Uzbekistan in the Aral Sea Basin. The designed water allowance of 0.40 l s−1 ha−1 was 46% higher than the 0.21 l s−1 ha−1 required in 2006. A ponding experiment conducted at two locations under typically shallow groundwater conditions showed that actual seepage losses in the major distributing canal (Pakhtakiyar) in the WUA were about 2% at one site and negative at the other. This does not support the present blanket recommendation of an additional 29% of water to compensate for anticipated seepage losses. Considering the effects of shallow groundwater the seasonal leaching requirements were estimated at 200 mm versus the 400 mm based on the blanket local recommendations for a 14 ha cotton field. However the actually applied water amounted to 670 mm which exceeds the calculated requirements by 235% and the local recommendation by 68%. The findings showed (i) excessive irrigation water supply and in turn high wastage owing to an underestimation of the potential shallow groundwater contribution (ii) overestimation of conveyance losses and (iii) excessive leaching due to outdated knowledge on leaching requirements when compared to standards. We suggest that the outdated water allowance the inaccurate estimation of the conveyance efficiency and excessive water applications during leaching cause a waste of precious fresh water and a rise in the shallow groundwater levels which consequently increases secondary soil salinity. The revision of irrigation and leaching norms combined with an improved knowledge on seepage dynamics under shallow groundwater levels is needed before any further recommendations can be made to the farmers in order to reach the objective of sustainable agriculture in the area. Copyright © 2011 John Wiley & Sons Ltd.
L'agriculture irriguée est très répandue dans les zones arides d'Asie centrale et constitue un facteur important de la sécurité alimentaire de la région. Toutefois les pratiques d'irrigation sur la base des règles habituelles établies pour la production de coton sur de grandes unités ne fournissent pas de directives adéquates pour les petits fermes maintenant répandues et qui produisent du coton du blé et du riz. Il en résulte la surexploitation excessive des eaux. L'article présente une étude de cas sur les pratiques de gestion des terres et des ressources en eau d'une association d'usagers de l'eau (AUE) d'une zone irriguée de 1885 ha. Ce travail a été effectué en 2006. L'AUE de Shomakhulum est situé dans la région de Khorezm en Ouzbékistan dans le bassin de la mer d'Aral. Le débit de projet correspondant aux règles habituelles de 0.40 l s−1 ha−1 a été alloué en 2006 soit 46% de plus élevé que le débit de projet de 0.21 l s−1 ha−1 correspondant au strict besoin des cultures. Une expérience d'infiltration pratiquée à deux endroits en condition typiques de nappe peu profonde a montré que les pertes réelles par infiltration dans le canal de distribution principal (Pakhtakiyar) de l'AUE ont été d'environ 2% sur un site et négative à l'autre (Note du traducteur: au sens ou la nappe recharge le canal). Ceci est en désaccord avec la recommandation générale de compenser les pertes par infiltration à hauteur de 29%. Considérant les effets de la faible profondeur de la nappe la dose de lessivage a été réévaluée à 200 mm par rapport aux 400 mm habituellement recommandés pour un champ de coton de 14 ha. Cependant l'eau effectivement allouée s'est élevée à 670 mm ce qui dépasse les besoins en eau des cultures de 235% et la recommandation habituelle de 68%. Les résultats ont montré (i) l'approvisionnement excessif en eau d'irrigation et la déperdition élevée en raison due à la sous-estimation de la contribution de la nappe superficielle (ii) la surestimation des pertes de transport et (iii) la dose de lessivage excessive due à des connaissances dépassées sur la question. Nous suggérons que l'allocation de l'eau désuète l'estimation inexacte de l'efficacité de transport et les doses de lessivage excessives occasionnent un gaspillage de l'eau douce si précieuse ainsi que la hausse du niveau des eaux souterraines avec pour conséquence l'augmentation de la salinité secondaire du sol. La révision des normes d'irrigation et de lessivage combinée à une meilleure connaissance sur la dynamique des infiltrations vers la nappe superficielle peu profonde sont nécessaires avant d'autres recommandations pour atteindre l'objectif d'une agriculture durable dans la région. Copyright
Escalating soil degradation caused by soil salinity and rising saline groundwater tables, limits crop production in the irrigated lowlands of arid Uzbekistan. Crop diversification is one option for obtaining more stable farm incomes while improving natural resource use and environmental sustainability. Although the agro-climatic conditions in the country allow growing a wide variety of crops, few crops (cotton, winter wheat, rice, maize) dominate the crop portfolio, which also reflects the restrictions imposed by the state. In the Khorezm region in northwest Uzbekistan, we examined the economic and ecological suitability of alternative crops in a stepwise approach. A literature review resulted in a list of about 30 crops that would theoretically fit the agro-climatic conditions in this region. For field research, five crops with a high potential were selected based on socio-economic (potential income) and bio-physical (potential yield, crop quality, options for soil improvement, water use efficiency) criteria. The crops included sorghum (Sorghum bicolor (L.) Moench), potato (Solanum tuberosum), the cash crop indigo (Indigofera tinctoria), and the food and feed crops mung bean (Vigna radiata) and sweet maize (Zea Mays L.). Field experiments were complemented with laboratory analyses and mathematical modeling for estimating the potential economic and ecological benefits from these crops. Three potato varieties from Germany out-yielded the local variety by at least 50%. Sorghum, indigo, maize and mung bean grew well on marginal lands and obtained very high revenues. Findings from the simulation runs demonstrate that crops such as maize for grain, potato and fodder crops could play an important role in coping with risks in drought years and for securing farm income. Field experiments and modeling results based on this extensive data set from Khorezm allow upscaling to regions in Central Asia with similar agro-climatic conditions.
In the irrigated areas of Uzbekistan the nitrogen (N) fertilizer efficiency in crop production is low, as N is partially leached
to the groundwater. The N-fertilizer use is still based on recommendations from Soviet times when fertilizer supply was subsidized
to maximize production at all costs. Also irrigation water is applied sub-optimally, and groundwater levels have been reported
to be of less than 1 m during the vegetation period. As substantial upward movement of salts from the groundwater is frequently
observed due to high evapotranspiration rates, it can be expected that nitrate from leached N fertilizer may also move in
the soil profile thus influencing the N balance of the soil. In this study we therefore estimated the groundwater contribution
to N-fertilization to improve the N management while sustaining yields and quality and reducing negative environmental effects
of groundwater nitrate. Nitrate in irrigation and groundwater was measured during spring and summer. Data were complemented
with field measurements of groundwater levels, irrigation and N-fertilizer amounts. With the CropSyst model, upward fluxes
of groundwater and evapotranspiration rates were derived, as we could not measure these in the field. We calculated the contribution
from the upward flux of nitrate-containing groundwater to the N content in the rooting zone. The difference between the simulated
actual evapotranspiration and the irrigated water amount was 335 mm. The average nitrate content in the groundwater was low
under summer crops (2 mg nitrate L−1) and higher under the spring crop (24 mg nitrate L−1). However, the temporal dynamics were very much linked to the irrigation and fertilization practices, and corresponded to
the changes in groundwater table depth: Almost immediately after fertilization, the nitrate content increased to up to 75
mg nitrate L−1 in spring. At the end of the growing period, the nitrate amounts had reached levels similar to those prior to fertilization.
A groundwater contribution of 355 mm and an average nitrate concentration of up to 75 mg nitrate L−1 would enhance the N stocks in the soil by up to 5–61 kg N ha−1. This is equivalent to one single fertilizer application event. However, in case farmers would rely on the input of N through
the groundwater to satisfy crop demand and consequently reduce N fertilizer application levels, the N concentrations in the
groundwater would reduce and become an unreliable source.
KeywordsGroundwater contribution-Supplemental N-fertilizer-Nitrate-Irrigated crop production-Evapotranspiration
Das Problem des schrumpfenden Aralsees ist hinlänglich bekannt, wesentliche Auswirkungen sind beschrieben und extensiver Bewässerungsfeldbau in Zentralasien wurde als Hauptursache identifiziert. Zur agrarindustriellen Produktion von Baumwolle wurde seit den frühen 1960er Jahren entlang der beiden großen Flüsse Amudarja und Syrdarja ein extensives Kanalnetzwerk etabliert. Damit sollte der stetig steigende Wasserbedarf der kontinuierlich wachsenden landwirtschaftlichen Nutzflächen in Zentralasien gedeckt werden. Bis Ende der 1980er Jahre wurde dieses System bis an die möglichen Grenzen der Tragfähigkeit erweitert. Nicht angepasster Wasserverbrauch führt zunehmend zu schweren ökologischen und ökonomischen Problemen in den Bewässerungsgebieten.
Land cover information is an essential parameter for many earth system models and studies. However, especially in Africa, rigorous, regional standardized and geometrical spatially explicit land cover data on medium scale is missing, or often inconsistent and outdated. In this study we employed well corrected 250-meter MODIS time-series observations from 2006 and 2007 to map land cover rigorously over the Volta Basin in West Africa, with focus on the Burkina Faso and Ghana respectively. We used the FAO land cover classification system (LCCS) standard [8] for the legend codes and 15-30 ASTER imagery as reference data to train the classification tree algorithm. Primary aim is to contribute to a continental African and standardized medium scale land over data base, with improved mapping accuracies. Therefore, the dataset presented here can be deemed interoperable that is between local scale studies, at finer resolutions, and 1-kilometer global land cover products.
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