Estimating ground water discharge by hydrograph separation.

Area of Science:

• Environmental Science
• Hydrology
• Geochemistry

Background:

• Iron Mountain, California, is a historical mining site with ongoing environmental concerns.
• Acid rock drainage and associated metal loading impact Boulder Creek water quality.
• Understanding water sources is crucial for managing pollution in mining-affected watersheds.

Purpose of the Study:

• To quantify groundwater's contribution to Boulder Creek's total flow during high-flow events.
• To assess the role of groundwater discharge in metals loading from Iron Mountain.
• To provide data supporting the development of remedial alternatives for acid rock drainage.

Main Methods:

• Employed a hydrograph separation technique to differentiate water sources in Boulder Creek.
• Collected extensive field data during high-flow storm events in winter months.
• Estimated groundwater discharge rates into the creek under peak flow conditions.

Main Results:

• Peak flow in Boulder Creek can exceed 22.7 m³/sec during high-flow storm events.
• Groundwater discharge was estimated to approach 0.31 m³/sec during the high-flow season.
• Hydrograph separation provided reasonable estimates of groundwater discharge when combined with field data.

Conclusions:

• Groundwater is a significant contributor to Boulder Creek's flow, especially during high-flow periods.
• Accurate estimation of groundwater discharge is vital for understanding metals loading.
• The findings support further investigations into metal loads from Iron Mountain's groundwater for remediation strategies.