Chloride Trends in Streams and Springs in the Spring Creek Watershed 1999-2024
By Dr. David DeWalle and Dr. Robert Carline
Table of Contents:
Introduction
List of Stream and Spring Monitoring Sites
Map of Spring Creek Watershed
Chloride Drinking Water and Aquatic Ecosystem Protection Criteria
Chloride Trends in Headwater Sites
Chloride Trends in Cedar Run Sub-Watershed Sites
Chloride Trends in Slab Cabin Run Sub-Watershed Sites
Chloride Trends in Thompson Run Sub-Watershed Sites
Chloride Trends in Mid-Watershed Spring Creek Monitoring Sites
Chloride Trends in Logan Branch Sub-Watershed Sites
Chloride Trends in Buffalo Run Sub-Watershed Sites
Chloride Trends in Lower-Watershed Spring Creek Monitoring Sites
Comparison of Chloride Statistics Among Sites for Period of Record and Recent Years (2023-24)
Rates of Change of Chloride Concentration at Sites for Period of Record
Summary
Introduction
This report is a synthesis and interpretation of available chloride data for springs and tributary streams in Spring Creek watershed collected over the past two decades by KWRC. The Keystone Water Resources Center (KWRC) is a 501c(3) non-profit led by a volunteer board of directors in State College, Pennsylvania. Funding for the project is provided by municipalities, non-profits and water and sewer authorities within the Spring Creek watershed. The mission of KWRC is to collect scientifically useful water quality and quantity data and make the data available to the public.
Data for this report were collected at 8 springs and 15 stream sites. Sampling began in 1999 at all but 3 sites. Site names and codes are listed in Table 1. Sampling occurred once in each season at stream baseflows. Some interruptions to sampling occurred due to Covid and funding issues in later years. Long-term trends in chloride concentrations in mg/L or parts per million (ppm) are shown over time for each site. Analysis of water samples for chloride was provided by Pennsylvania Department of Environmental Protection.
Spring Creek watershed is a complex karst system of inter-related springs and streams within five defined sub-drainages: Cedar Run, Thompson Run, Slab Cabin Run, Logan Branch and Buffalo Run which are shown in Figure 1. At least one stream and spring site were sampled in each sub-basin. Two major springs, Benner Spring and Big Spring, contribute flows directly to Spring Creek. The major urban-suburban area in the watershed is State College which includes parts of Slab Cabin Run and Thompson Run sub-basins. Data are given as a series of graphs showing chloride levels over time at each site as Spring Creek waters flow from headwaters near Boalsburg northward to the mouth of the watershed near Milesburg. U. S. EPA drinking water and aquatic ecosystem standards for chloride are also given. The report concludes with some figures showing comparisons of chloride averages and rates of change among sites and a brief summary and data interpretation by the author.
Monitoring Sites
STREAMS |
| SPRINGS |
|
BUL | Lower Buffalo Run | AXS | Axemann Spring |
BUU | Upper Buffalo Run | BLS | Blue Spring |
BVV | Buffalo Run at Valley View | BES | Benner Spring |
CEL | Cedar Run | BIS | Big Spring |
GGU | Galbraith Gap Run | COS | Continental Courts Spring |
LOL | Lower Logan Branch | LIS | Linden Hall Spring |
LOU | Upper Logan Branch | WAS | Walnut Spring |
MIL | Milbrook Marsh | WIS | Windy Hill Spring |
SLL | Lower Slab Cabin Run | ||
SLU | Upper Slab Cabin Run | ||
SPU | Upper Spring Creek | ||
SPA | Spring Creek at Axemann (USGS) | ||
SPH | Spring Creek at Houserville (USGS) | ||
SPM | Spring Creek at Milesburg (USGS) | ||
THL | Thompson Run |
Chloride Criteria for Drinking Water and Aquatic Ecosystems
Chloride Criteria | Purpose |
< 250 ppm | U.S. EPA secondary drinking water standard for humans, to control effects on taste, corrosion and damage to equipment. |
< 600 ppm | EPA recommended maximum, instantaneous, concentrations for protection of aquatic organisms |
< 150 ppm | EPA recommended 30-day mean concentration for protection of aquatic organisms, also PA DEP limit to protect aquatic macroinvertebrates |
Chloride in Headwaters of Spring Creek
Chloride Trends in Cedar Run Sub-Watershed
Chloride in Slab Cabin Run-Tributary to Spring Creek
Chloride in Thompson Run a Tributary to Slab Cabin Run
Chloride in Mid-Main Spring Creek
Chloride in Logan Branch Sub-Watershed
Chloride in Buffalo Run Sub-Watershed
Chloride Trends in Lower Main Spring Creek
Average Rates of Change of Chloride Concentration (ppm/yr) at Each Site for Period of Record
BLS | ns |
LIS | ns |
CEL | ns |
SLL | ns |
SLU | ns |
SPU | ns |
WIS | -0.47 |
GGU | -0.04 |
COS | 0.33 |
BUL | 0.33 |
BIS | 0.62 |
MIL | 0.69 |
BUU | 0.73 |
SPH | 0.77 |
LOL | 0.84 |
SPA | 0.84 |
SPM | 0.84 |
LOU | 0.88 |
AXS | 1.13 |
BVV | 1.31 |
THL | 1.39 |
WAS | 1.97 |
BES | 2.19 |
Trends determined by linear regression analysis. R2< 0.05 non-significant
Over the past 20 years chloride levels in Spring Creek watershed at stream baseflows were all below the U.S. EPA 250 ppm chloride drinking water standard. Also, average levels of chloride occurrences were all below the U.S. EPA and PA DEP standard of 150 ppm, as a 30 day-mean for protection of aquatic ecosystems. However, single occurrences of high chloride above 150 ppm Cl level were detected at four sites: Buffalo Valley View (BVV), Slab Cabin Upper (SLU), Thompson Run (THL), and Blue Spring (BLS).
Increasing chloride concentrations over the period of record were found at 9 of 15 stream monitoring sites and 5 of the 8 spring monitoring sites. Rates of chloride increases averaged +0.86 ppm Cl per year at these 9 stream sites and averaged +1.25 ppm per year in the 5 springs. The peak rate of increase of 2.2 ppm of Cl per year was found in Benner Spring (BES). Windy Hill Spring (WIS) showed a decreasing trend of chloride of -0.47 ppm Cl per year.
During the recent 2022-24 period, Spring Creek at the Axemann (SPA) site showed the highest mean chloride level (78 ppm) of the four main-stream Spring Creek sites sampled. At the current rate of chloride increase at that site, chloride levels at SPA would increase to 94 ppm over the next two decades. Among sites monitored, the sites contributing to higher mean chloride concentrations at SPA appear to be Thompson Run (THL), Slab Cabin Run (SLU and SLL), Walnut Spring (WAS), and Benner Spring (BES). Farther downstream in Bellefonte, major flows from Big Spring (BIS) at 27 ppm and Lower Logan Branch (LOL) site at 37 ppm appear to be helping to maintain a moderate chloride level of about 43-44 ppm all the way down to the lower Spring Creek (SPM) station.
Given that increasing trends in chloride levels were found at the majority of stream and spring sampling sites during baseflow, continued sampling at baseflows is needed. In addition, since chloride levels during high flows have not been assessed, additional sampling during stormflows is recommended in the future, especially during major snowmelt and rain-on-snow events when salting is used.
Acknowledgements
Dr. David DeWalle is a Emeritus Professor of Ecosystem Science and Management at the Pennsylvania State University.
Dr. Robert Carline is retired from the Pennsylvania Cooperative Fish and Wildlife Research Unit and an Adjunct Professor of Fisheries Science at Pennsylvania State University.
Both individuals serve on the Keystone Water Resources Center Board. The Keystone Water Resources Center monitors water resources in the Spring Creek Watershed. Data was compiled from annual reports in September 2025.
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