A Water–Energy Simulation Framework for Designing PV-Based Irrigation Supply Systems Under Transboundary Basin Constrains: The case of Samarkand

Water-Energy-Food (WEF) nexus challenges in Central Asia are intensifying because of climate change, increasing irrigation demand, and escalating pressures in transboundary river basins. Agriculture production in the economy of Uzbekistan plays an important role in sustainable development of the nation, accounting for 25 % of the country's GDP. Although the Zarafshan river is primarily shared between Tajikistan and Uzbekistan, upstream hydropower development, seasonal flow variability, and rising temperatures are increasingly constraining water availability for agriculture in downstream regions such as Samarkand in Uzbekistan. The Samarkand region, which relies heavily on pumped irrigation for cotton and wheat production, faces acute summer water shortages and growing dependence on grid-powered and diesel base pumping systems. These challenges underscore the necessity for resilient, low-carbon irrigation energy solutions. This study introduces water-energy simulation framework to investigate the optimization of pumping capacity and reservoir storage for efficient solar PV-powered irrigation systems. Crop water requirements are estimated using the FAO Penman-Monteith method. Monthly water-energy balances are simulated for various pumping durations (6, 8, 12, 18, 24 hrs/day), reservoir capacities and pumping heads. A comparative analysis of PV and grid scenarios assesses the role of reservoir storage in mitigating solar variability, reducing required PV capacity, and determining pump sizing. In addition to the technical assessment, the study incorporates a comprehensive economic analysis including life-cycle cost (LCC), cost-benefit analysis, and environmental impact assessment based on CO₂ emissions from the grid and diesel-based pumping.

The expected outcomes will identify optimal combinations of PV size, reservoir volume, and pumping discharge that minimize costs, improve energy performance, and reduce emissions. By linking system design to WEF nexus challenges in a transboundary basin, this research aims to support sustainable, energy-efficient irrigation strategies for the Samarkand region.

 

Keywords: Zarafshan River Basin, Transboundary water management, Water–Energy–Food Nexus, Solar-powered irrigation, Pumping–reservoir optimization, Water–energy balance, Life-cycle cost analysis, Cost–benefit ratio, CO₂ emissions, Sustainable agriculture