Scientific Investigations Report 2008–5132
Continued population growth and land development for commercial, industrial, and residential uses have created concerns regarding the future supply of potable water and the quantity of ground water discharging to streams in the area of Interstate 495 in eastern Massachusetts. Two ground-water models developed in 2002–2004 for the Assabet and Upper Charles River Basins were used to simulate water supply and land-use scenarios relevant for the entire Interstate-495 corridor. Future population growth, water demands, and commercial and residential growth were projected for year 2030 by the Metropolitan Area Planning Council. To assess the effects of future development on subbasin streamflows, seven scenarios were simulated by using existing computer-based ground-water-flow models with the data projected for year 2030.
The scenarios incorporate three categories of projected 2030 water- and land-use data: (1) 2030 water use, (2) 2030 land use, and (3) a combination of 2030 water use and 2030 land use. Hydrologic, land-use, and water-use data from 1997 through 2001 for the Assabet River Basin study and 1989 through 1998 for the Upper Charles River Basin study were used to represent current conditions—referred to as “basecase” conditions—in each basin to which each 2030 scenario was compared.
The effects of projected 2030 land- and water-use change on streamflows in the Assabet River Basin depended upon the time of year, the hydrologic position of the subbasin in the larger basin, and the relative areas of new commercial and residential development projected for a subbasin. Effects of water use and land use on streamflow were evaluated by comparing average monthly nonstorm streamflow (base flow) for March and September simulated by using the models. The greatest decreases in streamflow (up to 76 percent in one subbasin), compared to the basecase, occurred in September, when streamflows are naturally at their lowest level. By contrast, simulated March streamflows decreased less than 6.5 percent from basecase streamflows in all subbasins for all scenarios.
The simulations showed similar effects in the Upper Charles River Basin, but increased water use contributed to decreased simulated streamflow in most subbasins. Simulated changes in March streamflows for 2030 in the Upper Charles River Basin were within ± 6 percent of the basecase for all scenarios and subbasins. Percentage decreases in simulated September streamflows for 2030 were greater than in March but less than the September decreases that resulted for some subbasins in the Assabet River Basin. Only two subbasins of the Upper Charles River Basin had projected decreases greater than 5 percent. In the Mill River subbasin, the decrease was 11 percent, and in the Mine Brook subbasin, 6.6 percent.
Changes in water use and wastewater return flow generally were found to have the greatest effect in the summer months when streamflow and aquifer recharge rates are low and water use is high. September increases in main-stem streamflow of both basins were due mainly to increased discharge of treated effluent from wastewater-treatment facilities on the main-stem rivers. In the Assabet River Basin, wastewater-treatment-facility discharge became a smaller proportion of total streamflow with distance downstream. In contrast, wastewater-treatment facility discharge in the Upper Charles River Basin became a greater proportion of streamflow with distance downstream.
The effects of sewer-line extension and low-impact development on streamflows in two different subbasins of the Assabet River Basin also were simulated. The result of extending sewer lines with a corresponding decrease in septic-system return flow caused September streamflows to decrease as much as 15 percent in the Fort Pond Brook subbasin. The effect of low-impact development was simulated in the Hop Brook subbasin in areas projected for commercial development. In this simulation, the greater the area where low-impact development practices were applied, the less was the overall effect of development on recharge and nonstorm streamflow compared to the effects of traditional development practices for commercial areas. Low-impact development practices applied to individual parcels can potentially increase recharge in that parcel and consequently have a small effect on nonstorm streamflow out of the subbasin compared to lower recharge and nonstorm streamflows usually associated with traditional development practices in commercial areas. If low-impact development (as defined in this study) is applied to a greater number of surrounding parcels, however, the increase in recharge is additive with a correspondingly greater increase in nonstorm streamflow out of the subbasin compared to the effects on recharge and nonstorm streamflow associated with traditional development practices.
Posted January 8, 2009
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Carlson, C.S., DeSimone, L.A., Weiskel, P.K., 2008, Simulated effects of year 2030 water-use and land-use changes on streamflow near the Interstate-495 corridor, Assabet and Upper Charles River Basins, eastern Massachusetts: U.S. Geological Survey Scientific Investigations Report 2008–5132, 108 p.
Purpose and Scope
Previous Modeling Studies
Projected 2030 Land and Water Use
Model Simulation of Hydrologic Conditions in Year 2030
2030 Model Scenarios
Evaluation of 2030 Model Simulation Results
Assabet River Basin
Streamflow Changes by Subbasin
Major Results: Assabet River Basin
Upper Charles River Basin
Streamflow Changes by Subbasin
Major Results: Upper Charles River Basin
2030 Simulated Streamflows for Habitat Requirements
Assessment of Potential Effects of Low-Impact Development in Hop Brook Subbasin, Assabet River Basin—A Test Case
Assessment of Potential Effects of Sewering in Fort Pond Brook Subbasin, Assabet River Basin—A Test Case
Appendix 1. Methods Used to Develop Input Files for 2030 Model Scenarios
Appendix 2. Year 2030 monthly ground-water and surface-water withdrawals, Zone II limits for wells or the maximum withdrawal limit used for surface sources, Assabet and Upper Charles River basins, eastern Massachusetts
Appendix 3. Changes in average-annual water-budget inflows and outflows from basecase conditions for the seven scenarios by subbasin, Assabet River Basin, eastern Massachusetts
Appendix 4. Changes in March and September water-budget inflows and outflows from basecase for seven scenarios, by subbasin, Assabet River Basin, eastern Massachusetts
Appendix 5. Changes in average annual water-budget inflows and outflows from basecase for seven scenarios, by subbasin, Upper Charles River Basin, eastern Massachusetts
Appendix 6. Changes in March and September water-budget inflows and outflows from basecase for seven scenarios, by subbasin, Upper Charles River basin, eastern Massachusetts