Title

Dynamic models for conjunctive management of stream-aquifer systems of the glaciated Northeast

Date of Completion

January 1997

Keywords

Hydrology|Environmental Sciences|Operations Research

Degree

Ph.D.

Abstract

Dynamic simulation and simulation-optimization models are developed to evaluate conjunctive management of river-valley and outwash-plain stream-aquifer systems representative of the Northeastern United States. The objective of the conjunctive-management strategies is to maximize the sustained annual yields of ground-water based water-supply systems with constraints on allowable rates of streamflow depletion.^ Sustained yields increased as the number of planning periods per year increased because greater flexibility is added to the water-supply system by allowing for greater flexibility in the time-varying pumping schedules. However, many of the formulations that were constructed to maximize total annual yields resulted in highly variable pumping strategies through the year as the number of planning periods was increased.^ An important goal of water-resource supply systems is to provide nearly constant rates of water supplies over time. Methods that were shown to be useful in decreasing supply variability during a year while meeting streamflow-depletion targets were to reduce the upper bounds on pumping rates, to use wells located at large distances from the stream, and to use multiple withdrawal wells and artificial recharge.^ Sustained, constant annual yields were shown to increase from systems consisting of single withdrawal wells to systems consisting of multiple withdrawal wells and, then, to systems consisting of both withdrawal and injection wells. The use of multiple wells resulted in from 7 to 43 percent greater constant annual yields than those of the single-well formulations for the same streamflow-depletion constraints in the river-valley and outwash-plain systems that were evaluated.^ Artificial recharge is not a widely practiced management strategy in the Northeast. However, this research has shown that artificial recharge can increase net yields of a ground-water based water-supply system when combined with withdrawal wells. When artificial recharge was added to formulations for both the river-valley and outwash-plain systems, constant annual yields increased even further over those found by use of withdrawal wells only, and were limited only by the upper bounds on pumping specified in the formulations. ^