SP 3 - Water quality and water demand

The rapid change of land use systems in the Tarim basin over the last decade (irrigated agriculture for cash crop production) has substantially affected both quantity and quality of surface waters and groundwaters. Subproject 3 (SP3) focuses on these irrigated land use systems in the region of Aksu/Aral. In a nested approach, SP3 will consider different investigation areas beginning with crop water requirements on the field scale over yield production and water consumption on the farm level up to qualitative and quantitative hydrological/hydrodynamic computations for the whole Tarim River. On the plot scale for three sites differently affected by salinization, statements about water requirement and water quality will be achieved by crop modeling and by developing deficit irrigation strategies. The scientific finding will result in a sensor-controlled irrigation system for water saving production. The local scale will investigate the hydrology, salinity of soils and biomass production. This work comprises the calculation of salt fluxes in and out of the irrigation schemes and salt concentration in soils, biomass production, related water demand and water allocation and application along the salinization gradient from the upper to the lower reaches of the Tarim River.

Upscaling to the regional scale (about 200 km²) requires a scientific framework, which combines model output with remote sensing data in order to get validated and thus reliable results. Therefore, land  use, biomass production, LAI and evaporation will be mapped by satellite imagery and the outcome will be compared to the results of simulation models. By using calibrated water balance and ground water models, it is possible to determine the soil conditions and to perform a vulnerability analysis. Spectroscopy will be tested as a tool for assessing soil salinization status and to upscale these results to the regional scale. For different scenarios of landuse systems and related irrigation strategies the water availability, distribution and water quality will be finally modeled for Aksu/Aral oasis region.

A hydrodynamic model can estimate water quantity and quality along the Tarim River (1000 km) in consideration of groundwater levels and groundwater quality. For this task, large-scale mappings of land use systems, biomass and evapotranspiration rates (regional water balances) by satellite imagery will be available. Agricultural land use scenarios along the Tarim River will be implemented based on the integration of satellite-derived land use patterns and the hydrodynamic modelling tool. The entire hydrodynamic model enables the end-user or stakeholder to manage the water resources for optimizing their economical, ecological and social value.