Overallocation, increased demands, recognition and quantification of
environmental flows, and climate change have combined to make water
leasing a practical solution for addressing water shortages in many
watersheds. Leasing involves the temporary transfer of the consumptive
use portion of a water right to another user presumably for a higher
value purpose. Therefore, understanding the effect of water leasing on
river flow availability and river ecosystem protection is critical for
the watershed-scale water management. Numerical and computational
watershed simulation techniques coupled with water right models can
allow water managers to allocate water based on the legal framework
within the watershed, which in the western United States is typically
based on the prior appropriation doctrine. In this study, we simulate
the water trades on instream flow using an ASCE Penman-Monteith method
of evapotranspiration estimation on water right model. Using the Touchet
River basin in Washington State as a study location, we successfully
demonstrated simulation of water leases on instream flow. We choose the
Touchet River basin as a study location as this basin suffers frequent
water curtailment and has existing partnerships across diverse sectors
including water leasing markets to address this water resources concern.
This information will be extremely valuable for river ecosystem
protection and to watershed managers trying to plan future water
managements, water storage, and water trading projects.