Illustration of Water Withdrawal, Use, and Return Flows from the Scituate Reservoir, Rhode Island
A water budget is the accounting of water flow into and out of a defined area, such as a watershed. Water budgets are used to evaluate the availability and sustainability of water supply. Where, how much, and for what purpose water is used in an area affects its total water budget.
USGS, in cooperation with the Rhode Island Water Resources Board (RIWRB), created an animation of water flow that tracks water withdrawals, use, and return flows in Providence, Rhode Island, and the surrounding communities during the summer. This animation of flow incorporates reported withdrawal and return-flow data as well as estimates of other components of the water budget that lack reported information.
The Scituate Reservoir in Rhode Island, with storage of 37 billion gallons of water, is the state’s largest inland water body. The reservoir’s watershed drains 93 square miles in central Rhode Island and comprises about 9% of the state’s land area. Providence Water withdraws approximately 70 million gallons of water daily from the Scituate Reservoir to provide drinking water for nearly 60% of the state’s population. The utility distributes water to domestic (residential), commercial, and industrial users, which are manufacturing facilities that use water to fabricate, process, wash, and cool. Providence Water also sells water wholesale to other public suppliers in surrounding towns that distribute water to their respective customers.
The USGS compiled the water withdrawal and return-flow information necessary to create an illustration showing how water flows across the landscape and generated estimates to fill in gaps. The animation is meant to illustrate the interaction of components important for watershed planning and to show that there could be different locations of water withdrawal, use, and return flow.
The illustration for end-to-end tracking begins with withdrawals by Providence Water from the Scituate Reservoir; includes water use by Providence Water customers and utilities that purchase their water; and ends with the water’s return to natural water bodies (surface water) via outfalls from wastewater-treatment plants or to groundwater via septic systems. For watershed planning purposes, it is important to note that return flows are in different watersheds than the Scituate Reservoir withdrawal.
This water movement is not a closed system. Along the way, some water is added by precipitation (infiltration and inflow) and some is lost by leaks or pipe ruptures and through evaporation, incorporation into products (such as manufactured beverages) or crops, or consumption by humans or animals (consumptive use). Public suppliers reporting to the RIWRB include an estimate of non-revenue water, which includes leakage, meter errors, irrigation of parks and public land, and other municipal water uses. However, these reported non-revenue water amounts and estimates of consumptive use do not capture all system losses and gains. Therefore, this illustration also includes estimates of other system losses and gains, which make up the difference between withdrawals from the Scituate Reservoir and estimated portions of reported return flows from wastewater-treatment facilities for water that originated from the Scituate Reservoir.
Learn more about the data supplied and methods used to estimate water volumes in this illustration.
