Identifying the Dominant Drivers of Hydrological Change in the Contiguous United States

Understanding the dominant drivers of hydrological change is essential for water resources management. Watersheds in the United States are experiencing different types of changes (e.g., wet gets wetter and dry gets drier); however, few studies have analyzed what drivers are responsible for these changes, and how the dominant drivers vary over time and as a function of the climate/water regime and land cover. This study uses a time-varying Budyko framework to quantify the relative importance of precipitation, potential evapotranspiration, and other factors (e.g., climate seasonality, agricultural drainage, and urbanization) in 889 watersheds in the contiguous United States from 1950 to 2009. Results show that watersheds that are getting wetter are primarily due to increases in precipitation. However, watersheds in dry climates that are getting drier are primarily due to other factors, while watersheds in wet climates that are getting drier are primarily due to precipitation. The drivers causing statistically significant streamflow trends vary depending on dominant land-use types. Temporally, the increasing effects of other factors are more pronounced after the 1980s in the Midwest. The dominant drivers of streamflow in the United States are time-varying instead of constant. This is consistent with non-stationary patterns of streamflow. The time-varying drivers provide information on the processes that are increasingly important and require the most attention in water resources management.

Automated summary

Understanding the dominant drivers of hydrological change is crucial for effective water resources management. This study in the United States analyzes 889 watersheds from 1950 to 2009 and finds that precipitation is the primary factor causing wetter conditions, while other factors dominate in dry climates. The study highlights the importance of considering varying drivers in different regions and time periods for sustainable water management.