The Potential of Adaptive Water Management Techniques in Wisconsin

Population growth, climate change, and other uncertainties pose a collective challenge to water management. Based on 14 global climate models using three emissions scenarios of the Intergovernmental Panel on Climate Change, projections for the State of Wisconsin indicate changes by the end of the century that could significantly affect groundwater-based water utilities. The vast variability of climate change and other uncertainties including population growth and demand fluctuations challenge the ability of water managers to predict future conditions.Specific adaptive water supply alternatives are proposed in this study that aim to enhance the ability of a groundwater-based supply system to operate under a wider range of future variability. Two fundamental means are used to reach this end: residential water usage reduction as a means to minimize vulnerability to potential water stresses and groundwater recharge as a means to mitigate exacerbation of water stresses. A city in Wisconsin currently considering expansion of its supply system is used to provide context to the study. The city's existing supply alternatives are used as baselines for comparisons to the proposed alternatives of this study.A residential water usage reduction program (based on technology updates alone, i.e., without any behavioral change) and groundwater recharge options are developed and assessed in the case-specific context. The city's existing alternatives are modified using the reduction program and groundwater recharge options to compose new, proposed alternatives. Data sources include existing research of residential water end-use, existing groundwater recharge practices in Wisconsin, the local water utility, the Census Bureau, and the Environmental Protection Agency. The existing and proposed alternatives are assessed within a multi-criteria decision analysis based on pairwise comparisons using a holistic selection of metrics and various weighting scenarios to represent the range of stakeholder value systems.The results demonstrate that a comprehensive program to reduce residential water usage can reduce monetary costs of a water supply system as follows: a 3% reduction in capital costs, 15% reduction to the present value of total costs over 10 years, and 23% reduction to the present value of total costs over 50 years. The largest cost savings are in ongoing operations and maintenance, including a reduction in the high energy costs associated with deep-aquifer wells. The reduction program provides significant benefits beyond the monetary, including environmental and social benefits. The water usage reduction provides a reduction of over 16% in energy usage for residential water heating, generating direct savings for the customers totaling over 1.3 million annually. Carbon emissions fall by 39 to 63%. Aquifer drawdowns are mitigated and surface water baseflows improve. When groundwater recharge is also added, capital costs increase while the present value of total costs over 50 years still decreases slightly, compared to the existing alternatives. The groundwater recharge greatly amplifies the benefits to aquifers and surface water baseflows.The study demonstrates that fundamental adaptive measures can improve water supply alternatives in terms of monetary cost, environmental impacts, and social benefits, including a reduction in energy consumption at both the utility and household levels. However, various barriers currently obstruct transitions toward the adaptive measures discussed. A series of context-specific recommendations are provided that are intended to remove existing barriers to change.