Coupling biophysical processes and water rights to simulate spatially distributed water use in an intensively managed hydrologic system

Abstract

Abstract. Humans have significantly altered the redistribution of water in intensively managed hydrologic systems, shifting the spatiotemporal patterns of surface water. Evaluating water availability requires integration of hydrologic processes and associated human influences. In this study, we summarize the development and evaluation of an extensible hydrologic model that explicitly integrates water rights to spatially distribute irrigation waters in a semi-arid agricultural region in the western US, using the Envision integrated modeling platform. The model captures both human and biophysical systems, particularly the diversion of water from the Boise River, which is the main water source that supports irrigated agriculture in this region. In agricultural areas, water demand is estimated as a function of crop type and local environmental conditions. Surface water to meet crop demand is diverted from the stream reaches, constrained by the amount of water available in the stream, the waterrights-appropriated amount, and the priority dates associated with particular places of use. Results, measured by flow rates at gaged stream and canal locations within the study area, suggest that the impacts of irrigation activities on the magnitude and timing of flows through this intensively managed system are well captured. The multi-year averaged diverted water from the Boise River matches observations well, reflecting the appropriation of water according to the water rights database. Because of the spatially explicit implementation of surface water diversion, the model can help diagnose places and times where water resources are likely insufficient to meet agricultural water demands, and inform future water management decisions.

Including Variability across Climate Change Projections in Assessing Impacts on Water Resources in an Intensively Managed Landscape

“…This research aims to examine the agricultural irrigation water demand and water scarcity under future climate change scenarios using the generated ensemble of climate change realizations. The work is built upon an integrated hydrologic model that incorporates hydrological processes and the irrigation activities which follow the local water rights [17].…”

“…For each scenario group, we use WXGN to create an ensemble of daily weather variables required as inputs to a previously developed model of a coupled human-hydrological system [17]. The analytical workflow summarizing how we use WXGN to create large ensembles of forcing variables is shown in Figure 2 and is briefly summarized here.…”

“…An integrated socio-hydrologic model that simulates spatially explicit water use based on local water rights is used to evaluate spatiotemporal patterns of water scarcity in the context of the climate scenarios described above. A detailed overview of the biophysical and water rights components of the model, the datasets used to parameterize boundary conditions, calibration to and verification against PAST data, and limitations of the model in the context of those calibration/verification exercises was previously described by [17]. Here we provide a brief overview of the key model components pertinent to this study.…”

“…The unsatisfied water is the difference between the amount of water demanded and allocated for each place of use in the model. Detailed descriptions of the calibration and validation processes and the underlying algorithms are described by [17].…”

“…Recent past data of the same forcing variables at Boise Air Terminal were obtained from the National Climatic Data Center and National Solar Radiation Database for the period 1981-2014. Other datasets used in the model, including water rights data, Lucky Peak reservoir inflow data, stream discharge data, land use data, and watershed boundaries, were described in detail in [17] and are summarized in Table 3.…”