Trends in Precipitation, Streamflow, and Evapotranspiration in the Great Plains of the United States

Abstract

Planning and strategic management of water resources are contingent on trends in water availability. In this study, the impact of decade-scale variations in annual and seasonal precipitation on streamflow and evapotranspiration ͑ET͒ were identified for 10 watersheds in Nebraska, Kansas, and Oklahoma. In the Great Plains, an upward trend in precipitation over the last two decades of the 20th Century had a strong impact on streamflow and a comparatively weaker impact on ET. Even though precipitation, streamflow, and ET amounts differed between watersheds, the trend due to the precipitation increase was similar for all watersheds. Increased precipitation led to a disproportionately large increase in streamflow and comparatively smaller increase in ET. On average, a 12% increase in annual precipitation led to a 64% increase in streamflow, but only a 5% increase in ET. The seasonal partitioning of the annual precipitation increase was, in most cases, biased toward the fall, winter, and spring, with little or no change during the hot summer months. The strong streamflow response indicated that planning and management of surface-water storage and supply can be critically impacted by decadelong trends in precipitation. The lack of significant increase in precipitation and streamflow during summer suggests that any existing shortages will likely remain despite the observed annual precipitation increase. The ET response suggests that dryland farming and ecosystem vitality could benefit from the increased precipitation in fall, winter, and spring, but the relative impacts are more modest compared to the streamflow response and do not occur during summer when potential ET is greatest. Finally, since the mid-1990s precipitation and streamflow in a number of Oklahoma watersheds have shown a gradual decline from peak values in the late 1980s toward more average conditions. This declining trend in streamflow may be important for planning and management of water resources systems that must meet an increasing demand for water by a growing society while at the same time considering environmental and recreational needs.

Controls on runoff generation and scale-dependence in a distributed hydrologic model

“…While our study is focused on a single basin, the watershed exhibits similar hydrologic behavior to other regions in the Great Plains (Garbretch et al, 2004). As a result, basin response characteristics identified in this study may be applicable to similar settings in the broader region.…”

Annual baseflow variations as influenced by climate variability and agricultural land use change in the Missouri River Basin

“…Based on data for 1960-2011, Norton et al (2014) indicated a slightly increasing trend for the mean of the total annual precipitation in the Missouri River Basin. Garbrecht et al (2004) studied two watersheds in Nebraska and showed an increase in precipitation in both watersheds based on data for 1895-2001. Rahmani et al (2015) indicated an increasing trend in precipitation for the majority of Kansas using data from 1890 to 2011.…”

Analysis of Evapotranspiration Variability and Trends in the Arabian Peninsula

“…Research was conducted to detect climate changes, trends and variability in various parts of the world utilizing some climate parameters such as air temperature, rainfall depth, reference evapotranspiration ET o and pan evapotranspiration ET p (Schwartz and Randall, 2003;Garbrecht et al, 2004;Hegerl et al, 2007;Fu et al, 2009;Saghravani et al, 2009;Hakan et al, 2010). ET o is of particular importance because it combine changes in many other climate parameters including temperature, radiation, humidity and wind speed.…”

“…It has, however, direct influence on hydrologic water balance, irrigation and drainage canal design, reservoir operation, potentials for rain-fed agricultural production and crop water requirements (Dinpashoh, 2006). Several studies conducted in North America have shown that some climate parameters are on the rise including ET o (Fehrman, 2007;Garbrecht et al, 2004;Szilagyi, 2001). Fehrman (2007) found an increasing trend in ET o over the Mississippi area and that most of ET o increase can be attributed to the increase in July.…”