Hydrologic Impacts of Climate and Land Use Changes in the West Fork San Jacinto River of Texas
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Changes to climate and land use/land cover (LULC) are expected to be a source of uncertainty to streamflows in the Gulf Coastal Plains of Texas. Additionally, the city of Houston, Texas, is expected to experience spreading urbanization and immense population growth over the coming century, reaching 10 million people by 2050. As population grows over the next century so does the need for water in a city where groundwater is not a viable resource due to land subsidence. The West Fork San Jacinto (WFSJ) River’s watershed is expected to undergo rapid urbanization as Houston continues to sprawl and the water supply reservoir located on the WFSJ River, Lake Conroe, will have an increased importance in the coming century. Within the WFSJ watershed, changes in LULC are highlighted by an increase of urban land cover from 5.39% in 1992 to 14.7% in 2011. With this, impervious cover increased from 3.10% to 4.01% of the total watershed area from 2001 to 2011. The WFSJ River’s historical streamflow was investigated using two stream gauges for the periods of October 1974 to September 2016 and October 1984 to September 2016 for the upstream and downstream stream gauges, respectively. Historical trends for these periods were investigated using the Seasonal-Trend decomposition procedure based on Loess (STL), flow distribution, Richards-Baker Flashiness Index, and flow distribution. STL results showed a significant downward trend in streamflow for 3, 5, and 7 year trends. The only significant trend found was for mean monthly streamflow at both locations. This is possibly an indicator that urbanization had yet to reach a tipping point within the iii watershed for the historical period, but may also indicate that streamflow data was inadequate for trend detection due to gaps in streamflow records. The Variable Infiltration Capacity (VIC) hydrological model was utilized to investigate future scenarios of LULC and climate. A baseline period of 2001 to 2010 was established for climate and LULC and a future period was set for 2080 to 2089. Future climate scenario was based on the Representative Concentration Pathway 8.5 (RCP8.5) and future LULC was based on the USGS LandCarbon A2 scenario. In total, four scenarios were ran using VIC: baseline, LULC change, climate change, and combined LULC and climate change. Under the LULC change scenario streamflows increased by 0.39% and 4.66% for spring and summer, respectively, but decreased by 0.64% and 6.76% for fall and winter, respectively. Under the climate change scenario, streamflows decreased by 38.96%, 56.79%, 76.06%, and 48.44% for winter, spring, summer, and fall, respectively. The combined LULC and climate change scenario also exhibited decreases by 34.75%, 44.31%, 68.90%, and 45.12% for winter, spring, summer, and fall, respectively. Decreases in precipitation and increases to temperatures associated with climate change create an environment that favors lower streamflows but LULC changes have the ability to counteract these decreases. The study highlighted the uncertainty facing the water resources of the WFSJ watershed and Lake Conroe. The results indicate that less water will be available for the growing Houston metropolitan area.
West Fork San Jacinto
Murray, Jason Michael (2018). Hydrologic Impacts of Climate and Land Use Changes in the West Fork San Jacinto River of Texas. Master's thesis, Texas A & M University. Available electronically from