Hydrogeology of the Beaver Kill Basin in Sullivan, Delaware, and Ulster Counties, New York

Water-Resources Investigations Report 2000-4034
Prepared in cooperation with the Town of Rockland



The hydrogeology of the 299-square-mile Beaver Kill basin in the southwestern Catskill Mountains of southeastern New York is depicted in a surficial geologic map and five geologic sections, and is summarized through an analysis of low-flow statistics for the Beaver Kill and its major tributary, Willowemoc Creek. Surficial geologic data indicate that the most widespread geologic units within the basin are ablation and lodgment till. Large masses of ablation till as much as 450 feet thick were deposited as lateral embankments within the narrow Beaver Kill and Willowemoc Creek valleys and have displaced the modern stream courses by as much as 1,000 feet from the preglacial bedrock-valley axis.

Low-flow statistics for the Beaver Kill and Willowemoc Creeks indicate that the base flows (discharges that are exceeded 90 percent of the time) of these two streams—0.36 and 0.39 cubic feet per square mile,respectively—are the highest of 13 Catskill Mountain streams studied. High base flows elsewhere in the glaciated northeastern United States are generally associated with large stratified-drift aquifers, however, stratified drift in these two basins accounts for only about 5 percent and 4.4 percent of their respective surface areas, respectively. The high base flows in these two basins appear to correlate with an equally high percentage of massive sandstone members of the Catskill Formation, which underlies the entire region. Ground-water seepage from these sandstone members may be responsible for the high base flows of these two streams.

Suggested Citation

Reynolds, R.J., 2000, Hydrogeology of the Beaver Kill basin in Sullivan, Delaware, and Ulster Counties, New York: U.S. Geological Survey Water-Resources Investigations Report 2000–4034, 23 p., https://pubs.er.usgs.gov/publication/wri004034.

Table of Contents

  • Abstract
  • Introduction
  • Geology
  • Hydrology
  • Summary
  • Selected references
Publication type Report
Publication Subtype USGS Numbered Series
Title Hydrogeology of the Beaver Kill Basin in Sullivan, Delaware, and Ulster Counties, New York
Series title Water-Resources Investigations Report
Series number 2000-4034
DOI 10.3133/wri004034
Year Published 2000
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) New York Water Science Center
Description iv, 23 p.
Online Only (Y/N) N
Additional Online Files (Y/N) N
Google Analytic Metrics Metrics page
Additional publication details