资源环境科技发展态势分析平台

The Southeastern United States experiences recurring hydrological droughts, which can reduce water availability and result in water deficits. Long-term monitoring data from Panola Mountain Research Watershed, a small, forested, seasonally water-limited watershed near Atlanta, GA, was used to quantify interactions of climatic variability with shallow and deep storage and evapotranspiration. Watershed storage (WS) and actual evapotranspiration (AET) were estimated monthly from 1985 through 2015 using a relationship with baseflow and a water-budget approach, respectively. A watershed shallow storage (SS) water budget, based on soil moisture profile data, indicated a transition from recharge to surplus as dormant season SS increased to field capacity, and a transition from utilization of stored water to water deficits as growing season SS declined toward its wilting point. Deeper storage appeared unavailable to AET during dry conditions. The majority of deeper storage recharge occurred during the dormant season and required SS to be near field capacity. WS was an effective drought indicator. Growing season droughts typically occurred when WS was below normal at the end of the dormant season and growing season precipitation (P) was below or near normal. A hydrologic persistence analysis showed that monthly month-standardized WS was significantly correlated (p-value<0.05) with past monthly month-standardized WS for the previous 19 months and with past monthly P for the previous 11 months, indicating the importance of past hydrologic conditions on WS. These findings allowed assessment of expected climatic changes on the water cycle, which included effects on future recharge, water deficits, and drought occurrence.

Plain Language Summary Drought is the greatest recurring natural disaster in North America, resulting in reduced streamflows that are necessary for human use and aquatic plants and animals and shortages in shallow soil water that are necessary for plant growth and health. Monthly changes in storage of water in shallow and deep soils were estimated at a small, forested research watershed near Atlanta, Georgia to understand the relationships between shallow and deep storage and summertime drought occurrence. Summertime droughts occurred when springtime water storage in deeper soils was below normal and summertime rain was either near or below normal. Water storage in deeper soils was predominantly replenished by rain in the winter, but only after shallow soils were first wetted up. Deeper soils were rarely replenished during the summertime because most of the summertime rain that replenished water in shallow storage was evaporated or used by plants. These observations can be used to better understand conditions that result in drought in the Southeastern U.S. Expected climatic change in this region can affect the future occurrence of droughts by changing the amount of replenishment of water in deep soils in the winter and resulting in larger shortages in shallow soil water in the summer.