Status of Ground Water Banking in Idaho

Abstract

In the arid western United States, most water systems are fully allocated. Water for new uses must usually be obtained through reallocation of water that has already been claimed and assigned within prior appropriation. In Idaho, new allocations of ground water were made until approximately 1990. Since then, new uses have nearly always been met by reallocation, via prior appropriation water‐rights transfers or the operation of the Idaho Water Supply Bank. Using number of allocations or reallocations per year as a proxy for the effectiveness of allocation mechanisms, it appears that transfers and the Bank have not adequately served the needs of society. This indicates that Idaho's allocation of ground water resources is inefficient; that is, that total benefit to society could be improved by mechanisms that more readily facilitate reallocation of water. It appears that improvements to ground water banking could be made within the scope of existing Idaho water‐banking statutes, to improve the allocation of resources, reduce conflict and facilitate economic growth.

Groundwater banking: opportunities and management challenges

“…Where some of the recharged water is lost by leakage or other means, a discount could be applied to withdrawals (Contor, 2009(Contor, , 2010. Less than 100% of the recharged water may be allowed to be recovered.…”

“…For example, if maintenance of dryseason spring flows is a limiting factor, then wet-season recharge may not offset additional dryseason abstractions in the vicinity of the springs. Contor (2009Contor ( , 2010 proposed the use of surface-water-aquifer-response functions that would equalize the hydrologic values of recharge and abstraction with respect to time and location. Groundwater modeling can be employed to assess the impacts of proposed recharge and subsequent withdrawals on surface-water bodies and the aquifer.…”

“…Depending upon local circumstances, a substantial discount may have to be applied to avoid adverse impacts if they are to occur during dry periods when surface-water bodies are most vulnerable. From an economic perspective, the use of aquifer-response functions turns water into a homogenous quantity because the withdrawal point and time no longer make a difference with respect to surface-water impacts (Contor, 2010). The lack of a link between the banking system and the limitations of the physical system can be a cause of system breakdown.…”

“…The great storage volume available in aquifers is taken advantage of to store excess water for later use (typically surface water), which might otherwise not be put to beneficial use. Groundwater banking also includes regulatory storage-type aquifer recovery and storage (ASR) systems, in which injection of water into any aquifer confers a later right to withdraw the water (Maliva & Missimer, 2008, 2010. Groundwater banking systems typically store water in overdrawn freshwater aquifers.…”