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Estimated Water Use and Availability in the Lower Blackstone River Basin, Northern Rhode Island and South-Central Massachusetts, 1995–99

By LORA K. BARLOW

Water-Resources Investigations Report 03-4190

ABSTRACT

The Blackstone River basin includes approximately 475 square miles in northern Rhode Island and south-central Massachusetts. The study area (198 square miles) comprises six subbasins of the lower Blackstone River basin. The estimated population for the study period 1995–99 was 149,651 persons. Water-use data including withdrawals, use, and return flows for the study area were collected. Withdrawals averaged 29.869 million gallons per day (Mgal/d) with an estimated 12.327 Mgal/d exported and an estimated 2.852 Mgal/d imported; this resulted in a net export of 9.475 Mgal/d. Public-supply withdrawals were 22.694 Mgal/d and self-supply withdrawals were 7.170 Mgal/d, which is about 24 percent of total withdrawals. Two users withdrew 4.418 Mgal/d of the 7.170 Mgal/d of self-supply withdrawals. Total water use averaged 20.388 Mgal/d. The largest aggregate water use was for domestic supply (10.113 Mgal/d, 50 percent of total water use), followed by industrial water use (4.127 Mgal/d, 20 percent), commercial water use (4.026 Mgal/d, 20 percent), non-account water use (1.866 Mgal/d, 9 percent) and agricultural water use (0.252 Mgal/d, 1 percent). Wastewater disposal averaged 15.219 Mgal/d with 10.395 Mgal/d or 68 percent disposed at National Pollution Discharge Elimination System (NPDES) outfalls for municipal wastewater-treatment facilities. The remaining 4.824 Mgal/d or 32 percent was self-disposed, 1.164 Mgal/d of which was disposed through commercial and industrial NPDES outfalls.

Water availability (base flow plus safe-yield estimates minus streamflow criteria) was estimated for the low-flow period, which included June, July, August, and September. The median base flow for the low-flow period from 1957 to 1999 was estimated at 0.62 Mgal/d per square mile for sand and gravel deposits and 0.19 Mgal/d per square mile for till deposits. Safe-yield estimates for public-supply reservoirs totaled 20.2 Mgal/d. When the 7-day, 10-year low flow (7Q10) was subtracted from base flow, an estimated median rate of 50.5 Mgal/d of water was available for the basin during August, the lowest base-flow month. In addition, basin-wide water-availability estimates were calculated with and without streamflow criteria for each month of the low-flow period at the 75th, 50th, and 25th percentiles of base flow. These water availability estimates ranged from 42.3 to 181.7 Mgal/d in June; 20.2 to 96.7 Mgal/d in July; 20.2 to 85.4 Mgal/d in August, and 20.2 to 97.5 Mgal/d in September. Base flow was less than the Aquatic Base Flow (ABF), minimum flow considered adequate to protect aquatic fauna, from July through September at the 25th percentile and in August and September at the 50th percentile.

A basin-stress ratio, which is equal to total withdrawals divided by water availability, was also calculated. The basin-stress ratio for August at the 50th percentile of base flow minus the 7Q10 was 0.68 for the study area. For individual subbasins, the ratio ranged from 0.13 in the Chepachet River subbasin to 0.95 in the Abbot Run subbasin. In addition, basin-stress ratios with and without streamflow criteria for all four months of the low-flow period were calculated at the 75th, 50th, and 25th percentiles of base flow. These values ranged from 0.19 to 0.83 in June, 0.36 to 1.50 in July, 0.40 to 1.14 in August, and 0.31 to 0.78 in September. Ratios could not be calculated by using the ABF at the 50th and 25th percentiles in August and September because the estimated base flow was less than the ABF.

The depletion of the Blackstone River flows by Cumberland Water Department Manville well no. 1 in Rhode Island was estimated with the computer program STRMDEPL and specified daily pumping rates. STRMDEPL uses analytical solutions to calculate time-varying rates of streamflow depletion caused by pumping at wells. Results show that streamflow depletions were about 97 percent of average daily pumping rates for 1995 through 1999. Relative streamflow depletions for six public-supply wells with different aquifer properties and distances to a stream—Cumberland Water Department Manville wells no. 1 and no. 2; Pawtucket wells no. 2, 3, and 4; and Lincoln Lonsdale well no. 4— were simulated with a constant pumping rate to illustrate the effect different aquifer properties and distance have on depletion. After 30 days of simulated pumping, relative streamflow depletions for the six wells were 90, 91, 65, 71, 59, and 82 percent of withdrawals, respectively.

A long-term hydrologic budget was calculated for the period 1957–99. Water-withdrawal and wastewater-return-flow data used in the hydrologic budget were from 1995 through 1999. Total inflows and outflows for the entire study area were 815.83 Mgal/d. Precipitation, streamflow from upstream subbasins, and wastewater-return flow constituted 55, 43, and 2 percent of the total inflow, respectively. Evapotranspiration, streamflow out of the basin, and withdrawals constituted 24, 72, and 4 percent of the total outflow, respectively.

CONTENTS

Abstract

Introduction

Purpose and Scope

Previous Investigations

Description of the Study Area

Sand and Gravel Aquifers and Ground-Water Reservoirs

Surface Water

Climate

Population

Land Use and Land Cover

Acknowledgments

Water Use

Water Supply

Public Supply

Self-Supply

Aggregate Water Use by Category

Domestic

Public Supply

Self-Supply

Commercial

Public Supply

Self-Supply

Industrial

Public Supply

Self-Supply

Agricultural and Golf-Course Irrigation

Consumptive and Non-Account Use

Electric Power Generation

Wastewater-Return Flows

Public Disposal

Wastewater Imports and Exports

Infiltration and Inflow Estimates

Self-Disposal

Total Return Flows

Water-Use Summary

Water Availability

Streamflow-Gaging Stations Used in Analysis

Method Used to Estimate Base-Flow Volume

Safe-Yield Analysis for Public-Supply Reservoirs

Evaluation of Water Availability and Basin Stress

Streamflow Depletion by Ground-Water Withdrawals

Water Budget

Inflow

Outflow

Summary and Conclusions

References Cited

Glossary

Appendix 1. SIC code estimates by minor civil division

Appendix 2. Water-Use Case Study–Cumberland, Rhode Island

FIGURES

1-6. Maps showing:

1. Blackstone River basin and study area, northern Rhode Island and south-central Massachusetts

2. Distribution of sand and gravel and till deposits, and ground-water reservoirs as named by the Rhode Island Water Resources Board (Rhode Island portion only) in the lower Blackstone River basin

3. Streamflow-gaging stations and public-supply reservoirs within the lower Blackstone River basin

4. Estimated population by town and subbasin in the lower Blackstone River basin, 1995–99

5. Land use in 1995 in the lower Blackstone River basin

6. Public-supply wells and surface-water-intake locations within the lower Blackstone River basin

7. Graph showing public- and self-supply water use by category in the lower Blackstone River basin for the period 1995–99: ( A ) domestic, ( B ) commercial, ( C ) industrial, and ( D ) agricultural

8–10. Maps showing:

8. Power-generation facilities within the lower Blackstone River basin

9. Outfall locations for wastewater-treatment facilities serving towns within the lower Blackstone River basin

10. National Pollution Discharge Elimination System outfalls for commercial and industrial facilities within the lower Blackstone River basin

11. Diagram showing water withdrawals (supply), use, and return flow (disposal) for the lower lackstone River basin

12. Graph showing available base flow calculated as base flow minus minimum streamflow according to two criteria, the 7-day, 10-year low flow (7Q10) and Aquatic Base Flow (ABF), for June, July, August, and September for the period 1957–99 at the streamflow-gaging station at the Branch River at Forestdale, Rhode Island (U.S. Geological Survey station number 01111500)

13. Map showing subbasin stress indicated by the ratio of water withdrawals, 1995–99, to estimated water availability, 1957–99, during August; and graphs of water availability for June, July, August, and September for the six subbasins within the lower Blackstone River basin

14–15. Graphs showing:

14. Specified daily pumping rates at Cumberland Water Department Manville well no.1, Rhode Island, 1995–99, and calculated streamflow depletion in the nearby Blackstone River

15. Streamflow depletion as a percentage of well pumping rate ( Qs / Qw * 100) for six public-supply wells with different aquifer properties and distances to the stream in the lower Blackstone River basin. Q s is the rate of streamflow depletion (cubic foot per second)and Q w is the pumping rate of the well (cubic foot per second

 

TABLES

1. Land area and 5-year average population for each minor civil division within the lower Blackstone River basin, northern Rhode Island and south-central Massachusetts, 1995–99

2. Land area and population for minor civil divisions, water suppliers (major and minor), and wastewater-treatment facilities serving those municipalities within the lower Blackstone River basin, 1995–99

3. Total 5-year average population and population served by public-water systems and public-wastewater systems by minor civil division in the lower Blackstone River basin, 1995–99

4. Water withdrawals for public-supply wells and surface-water intakes by subbasin in the lower Blackstone River basin, 1995–99

5. Public-supply withdrawals, public-supply imports, public-supply exports, public-supply use, self-supply use, and total estimated withdrawals by minor civil division and subbasin in the lower Blackstone River basin, 1995–99

6. Agricultural, commercial, and industrial land-use area by subbasin as a percentage of total land area for the category in each minor civil division for the lower Blackstone River basin

7. Total water use, public and self-supply, by category in the lower Blackstone River basin, 1995–99

8. Agricultural coefficients used to estimate livestock water use in the lower Blackstone River basin

9. Average return flow for wastewater-treatment facilities serving communities of the lower Blackstone River basin, 1995–99

10. Average return flow for National Pollution Discharge Elimination System outfall locations for the lower Blackstone River basin, 1995–99

11. Public disposal (estimated and metered) of wastewater, including imports, exports, and infiltration and inflow, self-disposal (onsite septic estimates and metered), and total return flows for the lower Blackstone River basin, 1995–99

12. Summary of estimated water withdrawals, imports, exports, use, non-account use, consumptive use, and return flow in the lower Blackstone River basin, 1995–99

13. U. S. Geological Survey streamflow-gaging stations in the lower Blackstone River basin

14. Available base-flow volumes calculated at the 50th percentile by the PART program minus minimum streamflows determined by two criteria, the 7-day, 10-year low flow and the Aquatic Base Flow, for the Branch River at Forestdale (01111500) for June, July, August, and September for the period 1957–99

15. Safe-yield estimates and 5-year average demand for surface-water reservoirs of three municipal water suppliers in the lower Blackstone River basin, 1995–99

16. Area of sand and gravel and till deposits and percent of sand and gravel deposits within the lower Blackstone River basin

17. Summary of water availability, defined as base flow plus safe-yield estimates, for June through September in the lower Blackstone River basin, 1957–99

18. Summary of water availability, defined as base flow by aquifer type plus safe yield, for June through September in the lower Blackstone River basin, 1957–99

19. Average water withdrawal rates for the low-flow period in the lower Blackstone River basin, 1995–99

20. Summary of basin-stress ratios for June through September in the lower Blackstone River basin, 1957–99

21. Selected public-supply wells, parameters used to calculate streamflow depletion with the program STRMDEPL, and streamflow depletion as a percentage of the well pumping rate at 10, 20, and 30 days after the start of pumping

22. Long-term average annual hydrologic water budget by subbasin for the lower Blackstone River basin, 1957–99



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The citation for this report, in USGS format, is as follows:

Barlow, L.K., 2003, Estimated Water Use and Availability in the Lower Blackstone River Basin, Northern Rhode Island and South-Central Massachusetts, 1995–99: U.S. Geological Survey Water-Resources Investigations Report 03-4190, 85 p.


 For more information about USGS activities in Massachusetts-Rhode Island District, visit the USGS Massachusetts-Rhode Island Home Page.


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