Optimal economic use of an aquifer over time is analyzed under conditions of economic growth, inequality of groundwater withdrawal and consumption, and availability of surface water and artificial recharge. The value of an aquifer as a natural water quality treatment facility is derived.

Because a water sample collected from a well is an integration of water from different depths along the well screen, measured concentrations can be biased if analyte concentrations are not uniform along the length of the well screen. The resulting concentration in the sample, therefore, is a function of variations in well‐screen inflow rate and analyte concentration with depth. A multiport sampler with seven short screened intervals was designed and used to investigate small‐scale vertical variations in water chemistry and aquifer hydraulic conductivity in ground water contaminated by leaded gasoline at Galloway Township, Atlantic County, New Jersey. The multiport samplers were used to collect independent samples from seven intervals within the screened zone that were flow‐rate weighted and integrated to simulate a 5‐foot‐long, 2.375‐inch‐outside‐diameter conventional wire‐wound screen. The integrations of the results of analyses of samples collected from two multiport samplers showed that a conventional 5‐foot‐long well screen would integrate contaminant concentrations over its length and resulted in an apparent contaminant concentration that was as little as 28 percent of the maximum concentration observed in the multiport sampler.

A simple model is developed for determining the socially optimum price to charge locationally differentiated irrigation districts for both surface and groundwater supplies. Steady-state conditions are assumed for groundwater conditions and water demand functions. A divergence between social and private optimums arises from the existence of unadjudicated rights to groundwater supplies. The social optimum can be achieved by an appropriately conceived taxing policy. Water prices, tax rates, and optimum lift levels are estimated for seven irrigation districts, members of a master water agency. (

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If a manager of a given water resource is uncertain of his power to set optimum stream standards or optimum effluent charges at every moment in time, there exist conditions, qualitatively identified, under which it may be dynamically more efficient for him to establish present water quality levels that will be optimum only at some future date than to try unsuccessfully to achieve optimum levels at every point in time. Excess demand functions and an aggregate nonlinear damage function are the conceptual underpinnings of this paper. (Key words: Water quality; dynamic efficiency; management)