Rain, snow, and irrigation are the natural sources of water that infiltrate the soil. Other sources of water include active injection, pipe leaks, and liquid disposal. The fraction of infiltrating water that drains below the plant root zone and reaches the water table is called recharge. In many locales, this recharge water can be a significant contributor to groundwater resources. Watersheds that are recharge zones are increasingly subject to governmental protections as the value of the groundwater resource increases. Besides groundwater quantity, recharge can affect groundwater quality. The recharge water may initially contain contaminants. (e.g., pipe leaks or liquid disposal) or the water may pass through buried wastes and mobilize contaminants. In either case, the recharge water can then transport the contaminants to the groundwater and affect water quality.
PNNL has been evaluating recharge rates for a variety of soil types and plant communities since the mid-1970s. We have analyzed methods to both increase recharge rates (for water resource purposes) and decrease rates (for buried waste isolation). We assist our clients in making informed decisions by using our laboratory, field modeling systems to:
- Collect multiyear datasets with which to test recharge model predictions
- Estimate recharge rates using experience, related field data, or numerical models
- Measure recharge rates directly
- Optimize surface cover design to minimize recharge
- Predict recharge rates for possible future waste site conditions
- Estimate the spatial distribution of recharge rates to serve as the upper boundary condition for groundwater models.