Investigation of Uncertainties in Surface Water Resource Assessment of Georgia’s State Water Plan

Abstract

As one of the three key components of state of Georgia’s state water plan, a surface water availability resource assessment (SWRA) involves three sequential steps, as follows: (1) synthesizing unimpaired flow (UIF) data by removing anthropogenic effects from streamflow observations, (2) developing instream flow protection thresholds based on the UIF data, and (3) assessing possible resource gaps based on UIF data, flow protection thresholds, and water demands. Uncertainties are embedded in the observed input data and development processes, and could be propagated through these steps. A legitimate question pertains to the reliability of the SWRA results since they may affect regional water development plans. In this study, the uncertainties in all input data and development processes of SWRA were identified and quantified through Monte Carlo simulations. Results at two typical nodes indicate that uncertainties associated with the derived UIF data, flow thresholds, and SWRA results are very limited. The largest uncertainty came from the flow data-filling process. The most efficient way to reduce the uncertainty in future resource assessments is to maintain relatively complete flow and water use records.