Due to climate change and increased human impact, water use and protection have become one of the major regional issues in Central Asia. As availability of surface water is decreasing and becoming erratic, the reliance and pressure on groundwater resources are continuously growing. That is also a case with the Pretashkent Transboundary Aquifer (PTBA), located between the Republic of Kazakhstan and Uzbekistan.
The Pretashkent Transboundary Aquifer (PTBA)
Groundwater withdrawal from the aquifer is increasing, responding to high demand for water supply and irrigation. Aquifer-sharing countries have started dialogue about water policy and management tools for the PTBA, including development of an operational numerical model. This model is required for better understanding of the aquifer dynamics.
For her MSc research, IGRAC Intern and GroundwatCH participant Ainur Kokimova aimed to develop a conceptual hydrogeological and a test numerical model of the PTBA based on available data. The model allowed to assess the presence of cross-border groundwater flow, estimate the potential amount of groundwater in the system and analyse the possibility of brackish/saline water leakage from top layers to the Pretashkent Transboundary Aquifer.
The model was developed using the Groundwater Modeling System software (GMS). The model input preparation, including transboundary harmonization is conducted using the datasets and information from the Committee of geology and hydrogeology of Kazakhstan and results of the “Governance of Groundwater Resources in Transboundary Aquifers” project (GGRETA). The conceptual model included the simplification of the groundwater system consisting of 6 layers. The conceptual model was converted into steady-state numerical.
Test model outcomes
The test model showed that groundwater circulation consists of downward and upward flows in the system. Downward flow dominates in higher elevation where hydraulic heads vary from 410 till 650 m. The upward flow was detected in lower elevation with heads reaching 350 m, especially in discharge zones to rivers. The predicted total amount of groundwater inflow in the system is about 1.9 million m3/day. Recharge in the inflow (97.5% of contribution to the total inflow) and river leakage in the outflow (61.0% of contribution to the total outflow) are two main terms of the flow budget. 0.66 million m3/day flows from Uzbekistan to Kazakhstan and 0.25 million m3/day from Kazakhstan to Uzbekistan in the PTBA system.
The result confirmed the presence of the transboundary groundwater flow. Two wells, namely 48(11tn) and 43(7tn), on the territory of Kazakhstan might abstract groundwater flowing from Uzbekistan. The simulation of saltwater leakage predicted potential decrease of groundwater quality in the PTBA in the distant future.
Video with Ainur Kokimova
The MSc thesis 'Developing a transboundary groundwater model in the water scarce region of Central Asia: a case study of the Pretashkent Transboundary Aquifer' is available for download.