USGS Monthly Groundwater News and Highlights: September 4, 2018

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Feature: Effect of spatial and temporal scale on simulated groundwater recharge investigations

What effect does scale have on modeling groundwater recharge estimated from large-scale climate data? We presume that modeling over smaller areas and shorter time scales allows us to simulate physical processes more realistically, and thus provide better forecasts for water management decisions. This hypothesis was investigated using a Soil Water Balance model of the upper Colorado River Basin, where some management decisions are based on a ten-year moving average. The authors found that differences in the amount of modeled groundwater recharge were substantial during some seasonal comparisons. But trends in recharge were almost identical across scales, leading to similar conclusions about change from "normal" recharge. Considering the uncertainty inherent in projected climate data, coarser spatial and longer temporal scale input data may be sufficient for water resources managers who need to understand changes in trends in groundwater recharge over water-year or longer time periods. Learn more about this recent USGS study.

Figure: Location of the upper Colorado River basin study area within the southwestern United States. Source: Tillman and others, 2018. Figure is in the public domain.