| Popis: |
Climatic and anthropogenic factors can have a significant influence on groundwater resources, calling into question the future quality and quantity of the commodity. In this chapter, we discuss current and emerging issues concerning groundwater scarcity. These concepts are demonstrated using a case study from an urban reservoir that serves as a stormwater conduit to the nearshore ocean. Quantitative estimates of groundwater interaction with the reservoir were determined via direct tracer techniques which are rarely, if ever, used by urban hydrologists. Continuous time-series records of dissolved 222Rn were collected to evaluate the volumetric percentage of groundwater within the reservoir from 2012 through 2013. Using high-resolution sampling, we are able to characterize groundwater and reservoir response on event and seasonal time scales, while also offering general assessments of the hydrologic conditions during the study. When rainfall was not occurring, evapotranspiration served as the primary driver of overall hydrologic characteristics, directly influencing the water table and subsequent groundwater discharged from the reservoir. However, during storm events, hydrologic factors influencing the amount of groundwater within the reservoir were found to be more complex, including event duration, magnitude, and antecedent conditions. Seasonally, rainfall patterns were largely responsible for the magnitude of groundwater present within the reservoir and quasi-related to peak export to the coastal ocean. Most notably, we observed a decline in the volumetric percentage of groundwater within the reservoir as a result of increased groundwater residence time within the aquifer—a likely function of reduced aquifer recharge that would result from more efficient stormwater management. |
