This paper employs the feedback method of optimal control to solve groundwater hydraulic management problems such as maintaining a target piezometric surface within a confined aquifer. The feedback model for groundwater hydraulic management consists of a modified version of the groundwater model SUTRA coupled to a dynamic programming optimization model. A quadratic criterion representing a weighted sum of squared deviations from a target piezometric surface was chosen as the objective function. Under this criterion, a set of feedback rules for predicting optimal pumping strategies for the next time period based on current piezometric head values are a by‐product of the solution. The computed feedback rule coefficients are used to derive the optimal pumping strategy for the groundwater hydraulic management problem. The feedback model is shown to be an inverse groundwater simulation model in that piezometric heads are used to determine the optimal pumping rate.

Some groundwater contains the naturally occurring radioactive gas, radon‐222 (radon). Radon dissolved in groundwater is released into indoor air when plumbed in water is agitated indoors. Radon released from domestic water typically contributes less than 2% of total indoor radon. This article describes the health risks from radon in domestic water and the efforts within the United States to regulate radon in drinking water. The U.S. National Research Council (NRC) found that the primary health risks from radon in domestic water are lung cancer and stomach cancer, primarily to ever‐smokers. Radon concentration in air could reach levels considered unsafe for underground miners at some water treatment facilities that aerate water as part of the treatment process. Inhalation of radon gas and its progeny may result in lung cancer (inhalation risk). An estimated 11% of the health risk is from direct ingestion of radon dissolved in drinking water (ingestion risk). The NRC found that radon is a greater source of cancer risk than any other regulated chemical in drinking water. Some ecological studies contradict using the linear nonthreshold (LNT) model to assess the health risks from exposure to radon at low levels typical of indoor air. The U.S. Environmental Protection Agency (EPA) relied on the LNT model to assess health risks and propose standards and goal for radon in drinking water. Some water utilities could opt for treatment to comply with the radon in drinking water standard. Some other water utilities might avoid treatment by adopting a multimedia approach to radon mitigation. The multimedia approach could be more cost‐effective and achieve greater health risk reduction. Noneconomic considerations may influence that decision. Health risk reduction and cost analyses (HRRCA) suggest that most of the benefits would accrue to ever‐smokers and smaller water systems could incur most of the costs.

In 1974, the U.S. Congress, through the Safe Drinking Water Act (SDWA), created the first‐ever mandatory national program to protect consumers from harmful contaminants in drinking water. There have been several amendments to the Act—the most recent in 1996. The SDWA requires the U.S. Environmental Protection Agency (EPA) to set national drinking water quality standards (DWQS). The EPA has set primary and secondary DWQS for chemical, physical, radiological, and microbiological contaminants listed in Tables and. More Americans are now served by water systems without health risk violations since the EPA began tracking violations around 1980.

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