Irrigation, Climate, and Groundwater Depletion in Agricultural Regions of the US

Abstract:

Groundwater is increasingly relied on as a critical resource for meeting irrigation water demands. This study quantifies trends in groundwater levels across the US, and determines correlations with irrigation water extraction and climate patterns. We focus on high productivity agricultural regions including the High Plains and the lower Mississippi. Our analysis of all USGS groundwater level records for wells deeper than 30 m indicates that groundwater levels declined across much of these areas between 1949 and 2009. We illustrate some of the dominant patterns in groundwater decline, and explore potential correlations between resource use and availability. We observe correlations between pumping rate and groundwater level in a majority of counties with significant irrigation, with some notable exceptions. To determine how climate corresponded to groundwater levels we performed a simple regression analysis in addition to using wavelet coherence for both annual precipitation and longer-term climate phenomena against groundwater level observations. Due to the focus on deep production wells, we found minimal correlation between groundwater and inter-annual precipitation patterns, though on average the wells correlated with the longer period climate patterns, and specifically with the PDO. The results from this study can be used to quantify relationships between irrigation water consumption, climate, and groundwater resources, and potentially to estimate water scarcity risks under projected irrigation demands and climate conditions.