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Estimating Daily Public Supply Water Use by Drinking Water Service Area in New Jersey

Scientific Investigations Report 2024-5061
Water Availability and Use Science Program
Prepared in cooperation with New Jersey Department of Environmental Protection
By:  and 
https://doi.org/10.3133/sir20245061

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Abstract

This report, prepared in cooperation with the New Jersey Department of Environmental Protection, presents a method for estimating daily public supply water use by drinking water service area systems for New Jersey. The ability to accurately estimate daily public supply water use could help water supply planners in New Jersey better understand and manage the state’s limited water resources and balance the competing needs for freshwater resources. Data sources for this work include daily public supply water-use data from 2016 through 2020 acquired from New Jersey American Water for 15 drinking water service areas and monthly data exported from the New Jersey Department of Environmental Protection’s online water transfer data model database (known as NJWaTr). The two datasets were compared by aggregating the daily data to a monthly timescale. Statistical regression analysis was applied to the daily data, along with climate data, to evaluate what factors are influential in estimating daily fluctuations and trends in daily public supply water use. Fifteen regression equations were developed, one for each of the 15 drinking water service area systems for which daily data were acquired. Regression equations for systems that had seasonal patterns performed better than equations for non-seasonal systems. For the test year (2020), the average adjusted coefficient of determination for the linear regression with autoregressive errors model among systems with seasonality was 0.78; the average adjusted coefficient of determination for the linear regression with autoregressive errors model among systems with little or no seasonality was 0.25. The effects of anomalous data in the regression analysis were examined by comparing adjusted coefficient of determination values when the atypical data points were removed versus when they were retained in the analysis. Overall, including the anomalous data did not have a large effect on the results, and thus the data were retained for this study. 

In addition to developing regression equations, all 589 unique drinking water service area systems in New Jersey were characterized based on socio-economic data and monthly water-use data from NJWaTr. Systems that are located near the New Jersey coast, serve populations larger than 1,970 people, or serve areas that have median property values over $256,250 tended to demonstrate seasonal water-use behaviors. Systems that have mostly urban residential land use tended to show little to no seasonal water-use behaviors. Finally, a method was developed to disaggregate monthly data to a daily timescale and was tested against systems for which daily data were not available. Two regression equation forms were developed to be applied to systems beyond the 15 systems from which the original equations were developed; one equation was developed for use when all drinking water service area systems showed little to no seasonality, and the other equation was developed for use when systems displayed seasonal behavior. 

To the extent possible, uncertainty and possible sources of error were identified and examined in relation to the regression model equations developed. Additional daily data from these 15 systems (over different years) and daily data from different systems could be used to further evaluate the results of the disaggregation through a comprehensive assessment of error. Further adjustments to the regression equations could be made, ultimately enhancing their accuracy. 

Suggested Citation

Shourds, J.L., and Scott, M.H., 2025, Estimating daily public supply water use by drinking water service area in New Jersey: U.S. Geological Survey Scientific Investigations Report 2024–5061, 90 p., https://doi.org/10.3133/sir20245061.

ISSN: 2328-0328 (online)

Study Area

Table of Contents

  • Preface
  • Acknowledgements
  • Abstract
  • Introduction
  • Purpose and Scope
  • Public Supply Water-Use Data in New Jersey
  • Drinking Water Service Area System Characterizations
  • Development of a Daily Water-Use Regression Model
  • Disaggregation of Monthly-to-Daily Water-Use Estimates
  • Summary
  • References Cited
  • Appendix 1. Drinking water service area systems characteristics for all 589 unique systems in New Jersey
Publication type Report
Publication Subtype USGS Numbered Series
Title Estimating daily public supply water use by drinking water service area in New Jersey
Series title Scientific Investigations Report
Series number 2024-5061
DOI 10.3133/sir20245061
Publication Date June 17, 2025
Year Published 2025
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) New Jersey Water Science Center
Description Report: xi, 90 p.; Appendix
Country United States
State New Jersey
Online Only (Y/N) Y
Additional Online Files (Y/N) Y
Additional publication details