Statistical Comparisons of Watershed-Scale Response to Climate Change in Selected Basins across the United States

In an earlier global climate-change study, air temperature and precipitation data for the entire twenty-first century simulated from five general circulation models were used as input to precalibrated watershed models for 14 selected basins across the United States. Simulated daily streamflow and energy output from the watershed models were used to compute a range of statistics. With a side-by-side comparison of the statistical analyses for the 14 basins, regional climatic and hydrologic trends over the twenty-first century could be qualitatively identified. Low-flow statistics (95% exceedance, 7-day mean annual minimum, and summer mean monthly streamflow) decreased for almost all basins. Annual maximum daily streamflow also decreased in all the basins, except for all four basins in California and the Pacific Northwest. An analysis of the supply of available energy and water for the basins indicated that ratios of evaporation to precipitation and potential evapotranspiration to precipitation for most of the basins will increase. Probability density functions (PDFs) were developed to assess the uncertainty and multimodality in the impact of climate change on mean annual streamflow variability. Kolmogorov?Smirnov tests showed significant differences between the beginning and ending twenty-first-century PDFs for most of the basins, with the exception of four basins that are located in the western United States. Almost none of the basin PDFs were normally distributed, and two basins in the upper Midwest had PDFs that were extremely dispersed and skewed

Simulating Climate and Landscape Effects on Hydrology using the Precipitation Runoff Modeling System in the Apalachicola-Chattahoochee-Flint River Basin, Southeastern USA

Proceedings of the 2013 Georgia Water Resources Conference, April 10-11, 2013, Athens, Georgia.To help environmental resource managers assess potential effects of climate change on ecosystems, the Southeast Regional Assessment Project (SERAP) began in 2009. One component of the SERAP is development and calibration of a set of multi-resolution hydrologic models of the Apalachicola-Chattahoochee-Flint (ACF) River Basin. The ACF River Basin is home to multiple fish and wildlife species of conservation concern, is regionally important for water supply, and has been a recent focus of environmental and climate-change research. Hydrologic models of varying spatial extents and resolutions are required to address varied local-to-regional water-resource management questions as required by the scope and limits of potential management actions. These models are developed using the U.S. Geological Survey Precipitation Runoff Modeling System (PRMS). A coarse-scale model developed for the ACF River Basin has a contributing area of approximately 50,700 km2; while, six fine-resolution PRMS models ranging in size from 396 km2 to 2,690 km2 are nested within the coarse-scale model, and have been developed for the following basins: the upper Chattahoochee, Chestatee, and Chipola Rivers, and Ichawaynochaway, Potato, and Spring Creeks. Both coarse- and fine-scale models simulate basin hydrology using daily time-steps, measured climatic data, and basin characteristics such as land cover and topography. Measured streamflow data are used to calibrate and evaluate computed basin hydrology. Land cover projections are used in conjunction with downscaled Global Climate Model results to simulate future hydrologic conditions for this set of models.Sponsored by: Georgia Environmental Protection Division; U.S. Department of Agriculture, Natural Resources Conservation Service; Georgia Institute of Technology, Georgia Water Resources Institute; The University of Georgia, Water Resources Faculty.This book was published by Warnell School of Forestry and Natural Resources, The University of Georgia, Athens, Georgia 30602-2152. The views and statements advanced in this publication are solely those of the authors and do not represent official views or policies of The University of Georgia, the Georgia Water Research Institute as authorized by the Water Research Institutes Authorization Act of 1990 (P.L. 101-307) or the other conference sponsors