MONITORING AND ASSESSING WATER AVAILABILITY IN THE HIGH PLAINS AQUIFER IN KANSAS
Changes in water-level – or the rate at which the water-level is changing – are considered the most direct and unequivocal measure of the impact of management strategies. In the Kansas HPA, water-level change is currently determined through an annual water level survey conducted each winter. The once-a-year manual measurements obtained in the survey are subject to errors from three major sources (in addition to the inherent accuracy and precision of the measurement itself): barometric pressure fluctuations, pumping interference, and incomplete recovery from the previous irrigation season. As a result, these measurements are only useful for discerning impacts over fairly large spatial (>township) and temporal (>10 yr) scales. This project has focused on identifying and reducing the uncertainties and inaccuracies involved in producing quantitative estimates of year-to-year changes in water level to identify impacts as rapidly as possible on scales relevant for aquifer management.
Telemetered, transducer-equipped wells were installed at three sites in the HPA in August 2007. At two sites, transducer records from nearby wells are available for comparison. Water-level responses to barometric pressure varies at the three sites, and are significant enough to require correction at two sites. Although identification of the fully recovered water level is vital for assessing water management strategies, full recovery has not been observed at any site over the monitoring period, necessitating use of recovery projection methods developed by Theis and Horner. These methods indicate two-stage recovery occurs at two of the sites, complicating the estimation of full recovery. Further refinement of water-level estimation procedures, combined with a calibrated budgetary approach incorporating water use and precipitation, appears to have potential for predicting and monitoring the effects of management on groundwater resources in a timely fashion.