Groundwater (GW) management is an essential element in irrigated agriculture. This paper analyzes the temporal dynamics of GW table and salinity in Khorezm, a region of Uzbekistan which is situated on the lower Amu Darya River in the Aral Sea Basin and suffering from severe soil salinization. We furthermore identify the critical areas for potential soil salinization by examining GW table and salinity measured during 1990-2000 in 1,972 wells, covering the entire region. Additionally, case studies were performed to assess the contribution of the GW to the soil salinization on a field scale. Over the entire area, GW was only moderately saline averaging 1.75±0.99 g l −1 However, GW levels were generally very shallow averaging 148±57 cm below the ground surface and thus likely to prompt secondary soil salinization. Three case studies where GW table, soil and GW salinity were closely monitored at the field scale, suggested that the elevated GW levels forced soil salinization by annually adding 3.5-14 t ha −1 of salts depending on the position and salinity of the GW table. Maps interpolated from the regional dataset revealed that GW was significantly shallower and more saline in the western and southern parts of Khorezm despite the presence of a drainage network which is rather uniformly distributed throughout the region. The results of the current study will assist the development of an improved drainage management in Khorezm.

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In this surface water modeling study, a new spatial evaluation for assessing the impact of urbanization was applied for the semi-arid watersheds intersecting with the Gaza coastal aquifer. The SWAT model was calibrated and validated in a semi-automated approach for stream flow in the main watersheds. The results show that the model could simulate water budget components adequately within the complex semi-arid watersheds.Linear relationships between the change in urban area and the corresponding change in surface runoff or percolation were concluded for the urbanized subbasins. The urbansurface runoff index (USI) and the urban-percolation index (UPI) were developed to represent a micro-level evaluation of different urban change scenarios in the subbasins.The global urban-surface runoff index (GUSI) and the global urban-percolation index (GUPI) were derived as macro-level factors reflecting the influence on the overall Gaza coastal aquifer due to urban area expansion.

Farming is the main livelihood activity in semi-arid rural West Africa, involving the largest portion of the population, contributing significantly to the regional economy and intimately intertwined with current environmental problems. Key vulnerabilities of the Sudan Savanna include its ecological fragility, institutional weakness, high levels of poverty and food insecurity, and political and economic instability, now aggravated by climate change. The characterization of current farming and cropping systems in the Sudan Savanna is the key for understanding and proposing meaningful adaptation strategies at the field, farm, local and national levels. This review begins by examining the agroecological (biophysical) profile, detailing climatic, edaphological and hydrological qualities. Next, the main socioeconomic features: demography, culture, and organizational and economic institutions are summarized, followed by a characterization of the main farming and cropping systems and associated management. The paper concludes by offering an outlook on targeted activities, interventions and strategies for cropping and farming systems to cope and adapt to climate change and variability, as well as soil fertility challenges within the current socio-ecological context.

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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, doublesided irrigation, and control of inflow through flow-measuring devices installed at farm gates, and adequate water pricing.