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Simulating Present and Future Groundwater/Surface-Water Interactions and Stream Temperatures in Beaver Creek, Kenai Peninsula, Alaska

Scientific Investigations Report 2024-5126
By: , , , , and 
https://doi.org/10.3133/sir20245126

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Abstract

In many places, coldwater ecosystems are facing increasing pressure from anthropogenic warming. This study examined stream temperatures and the water balance in the Beaver Creek watershed on the Kenai Peninsula in south-central Alaska—an area that is experiencing rapid warming. Low-gradient streams near the Kenai coast provide important spawning and rearing habitat for salmon but may be especially vulnerable to rising temperatures, because of long residence times, inflows from abundant riparian wetlands, and reliance on groundwater discharge that may also warm, or decrease in volume with rising evapotranspiration. In recent decades, observed maximum 7-day temperatures have consistently exceeded statistical (regression-based) projections. Here we simulate total streamflows and temperatures with a physics-based model that links the Soil Water Balance, MODFLOW 6 and SNTEMP simulation codes on a 7-day timestep. The model is based on existing data and groundwater levels, instream flows, and stream temperatures collected during 2019–23. Future climate scenarios were developed for 2023–50 from downscaled climate projections.

Results indicate that groundwater discharge is about 64 percent of the total streamflow during the months of May through September. Total streamflow and groundwater discharge are expected to remain similar to current conditions through 2050. Stream temperatures are expected to rise; by midcentury, near the Beaver Creek mouth the model predicts 34 to 63 additional days per year with average weekly temperatures above 13 degrees Celsius, 14 to 81 additional days with average weekly temperatures above 15 degrees Celsius, and routine exceedances of 20 degrees Celsius during the warmest periods. Projected stream temperatures vary spatially. Areas of high groundwater inflows in the lower main stem and some tributaries may be most resilient to warming air temperatures during dry conditions. During storm events, groundwater-dominated tributaries may have the coolest stream temperatures.

Suggested Citation

Leaf, A.T., Haserodt, M.J., Meyer, B.E., Westenbroek, S.M., and Koch, J.C., 2024, Simulating present and future groundwater/surface-water interactions and stream temperatures in Beaver Creek, Kenai Peninsula, Alaska: U.S. Geological Survey Scientific Investigations Report 2024–5126, 111 p., https://doi.org/10.3133/sir20245126.

ISSN: 2328-0328 (online)

Study Area

Table of Contents

  • Acknowledgments
  • Abstract
  • Introduction
  • Site Description and Hydrologic Setting
  • Field Data Collection
  • Groundwater Flow and Soil-Water-Balance Models
  • Stream Temperature Model
  • Parameter Estimation
  • Model Scenarios
  • Results and Discussion
  • Assumptions and Limitations
  • Summary and Conclusions
  • References Cited
  • Appendix 1. Glacial Geologic History of the Beaver Creek Basin and Interpretation into Model Layers
  • Appendix 2. GFLOW Model
  • Appendix 3  Soil-Water-Balance Model
  • Appendix 4. MODFLOW 6 Model Construction
  • Appendix 5. Stream Network Temperature Model Construction
  • Appendix 6. Parameter Estimation and Uncertainty Analysis
  • Appendix 7. Future Climate Scenarios
Publication type Report
Publication Subtype USGS Numbered Series
Title Simulating present and future groundwater/surface-water interactions and stream temperatures in Beaver Creek, Kenai Peninsula, Alaska
Series title Scientific Investigations Report
Series number 2024-5126
DOI 10.3133/sir20245126
Year Published 2024
Language English
Publisher U.S. Geological Survey
Publisher location Reston VA
Contributing office(s) Upper Midwest Water Science Center
Description Report: ix, 111 p.; 2 Data Releases; Dataset
Country United States
State Alaska
Other Geospatial Beaver Creek, Kenai Peninsula
Online Only (Y/N) Y
Additional Online Files (Y/N) N
Google Analytic Metrics Metrics page
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