Analytical modeling of irrigation and land use effects on streamflow in semi-arid conditions

- Streamflow simulation method for streams affected by GW pumping.
- New approach combines analytical consideration of GW pumping and land-use changes.
- Land-use and irrigation data aggregated to account for spatio-temporal variations.
- Calculations by Jenkins' model accurately represent stream depletion by 462 wells.
- Modeled streamflow of Frenchman Creek, Nebr., USA compares well with observations.

SummaryAvailability and uncertainty in input data are the primary constraints of groundwater modeling. Analytical models assimilate the key and important data, but capture the major traits of the watershed. We study a baseflow-dominated stream, Frenchman Creek in southwestern Nebraska, USA, which has experienced large streamflow reductions since the 1960s and is a subject of various actions on water rights appropriation. The new element of the model is simultaneous analytical consideration of groundwater pumping and land use change effects. Analytical stream depletion rate calculations by various methods show that pumping from the 462 irrigation wells in the basin consumed a large amount of baseflow. The simulated streamflow at the outlet of Frenchman Creek with minimal calibration compares favorably with observed streamflow and indicates the viability of an analytical approach to watersheds with limited hydrogeologic data.