FORECASTING CHANGES TO GROUNDWATER AND SURFACE WATER FLOW REGIMES IN WESTERN NEW YORK UNDER A CHANGING CLIMATE
MetadataShow full item record
While generally not receiving the same level of coverage and concern as arid regions, water-rich areas such as Western New York face unique hydrologic challenges under a changing climate. Predicted increases in precipitation and temperature are expected to significantly alter the hydrologic system of the region resulting in increased risk to urban infrastructure. These changes could lead to a wide range of stark deviations from the current hydrologic system including large changes to runoff, stream discharge, stream stage, and evapotranspiration rates. Increases in mean precipitation are predicted to result in rises in water table elevations leading to elevated risk of leaky combined sewer overflows, an event that significantly impacts the quality of surface water bodies. In order to assess both the hydrologic system as a whole and the future risk of leaky combined sewer overflows in Western New York, a novel, linked, three part modeling approach, consisting of climate, surface water, and groundwater models was developed. The modeling approach allows for the analysis of spatial and temporal changes to recharge, evapotranspiration, runoff, stream discharge, and water table elevation. The climate portion of the approach was modeled by the Mesoscale Model 5I -Community Climate Systems Model pairing (MM5I-CCSM) regional climate model which utilizes the A2 (high midcentury emissions) scenario. The MM5I-CCSM model is a product of dynamical downscaling whereby a finer scale regional climate model is imbedded in the framework of a coarser scale general circulation model which acts as the boundary conditions for the regional model. The surface water portion of the approach was modeled by the basin scale, lumped parameter model SWAT. SWAT simulates surface processes such as recharge, evapotranspiration, and runoff based off land surface characteristics and daily weather inputs from the regional climate model. MODFLOW was employed to represent the groundwater and surface water portions of the model domain. Daily values of recharge, evapotranspiration, and surface runoff were incorporated into the MODFLOW model from SWAT as transient boundary conditions. This three part approach includes the linkage of all three portions of the hydrologic system allowing for the assessment of surface water and groundwater flow regimes driven by climate model outputs. A baseline model was developed using historical weather and water level data from the year 2010 through 2014. Simulations from the historical model were compared against two future models driven by results from the dynamically downscaled climate model from 2045 through 2049 and 2065 through 2069. Model results from the future climate change scenarios suggest large spatial and temporal changes in surface water and groundwater flow regimes. Changes in surface water and groundwater processes are a direct result of climate model forecasted changes in precipitation, temperatures, solar radiation, wind speeds, and humidity. Results from the surface water model suggest mean annual increases in both recharge and evapotranspiration in the future however, spatial and temporal variabilities are large across the model domain. Changes in surface and groundwater processes resulted in highly variable changes in stream discharge relative to historical outputs. Generally, water table elevations are predicted to increase throughout the model domain in both future scenarios with the more distant future scenario experiencing the greater increases. Changes in water table elevations, from the historical period, vary across the model domain from slight decreases in some areas to large increases in others. Spatial variability in changes to groundwater elevations are a result of a number of factors including spatial and temporally varying weather patterns, variable surface characteristics resulting in area specific recharge and evapotranspiration rates, temporally varying stream elevations and discharge rates, and spatially varying aquifer geologic characteristics. Groundwater flow modeling identified areas at elevated risk of leaky combined sewer overflows caused by inundation of sewer lines from a rising water table. Groundwater and surface water modeling under future climate scenarios provides a representation of the highly interconnected hydrologic system of Western New York and the spatially and temporally varied responses to changes in the climate. This three-part approach allows for the analysis of flow regimes at the fine scale necessary to assist policy makers in locating areas that are potentially susceptible to the adverse hydrologic effects of climate change.