Analyzing Uncertainty and Risk in the Management of Water Resources for the Texas Water Development Board

The State of Texas updates its state water plan every 5 years to determine the water demand required to meet its growing population. The plan compiles forecasts of water deficits every decade over the 50 year planning horizon from regional water planning groups around the state and details water supply strategies and associated costs of implementation. To date, the plan has adopted deterministic predictions for population growth, water demand, water availability, etc. These predictions are, in reality, affected by multiple sources of uncertainties such as the impact of climate on water availability, uncertainty in population projections, variability in water usage, feasibility of the permitting process, societal concerns, cost of implementation, etc. The objective of this project was to develop a generalized and scalable methodology for addressing uncertainty and risk in water resources management both at the regional and the local water planning level. This framework captures key components of demand, supply and planning modules along with their associated uncertainties. The uncertainty in the water planning process is broken down into three primary categories: demand uncertainty, supply uncertainty, and uncertainty in water management strategies for meeting water shortages. Uncertainty in demand is related to the uncertainty in population projections and the per-capita usage rates and is characterized by using population projection scenarios and historical usage data. Uncertainty in supply is dominated by the uncertainty in future climate conditions, and is modeled using global circulation models and water availability models (WAMs). Strategies also vary in the degree of feasibility in permitting and future implementation. The final output from the analysis consists of scenarios for future demand and supply as well as reliabilities of different water management strategies, all of which can be used by decision-makers to make more robust decisions when planning for water needs of the future.