Simplified Stream Accretion Modeling for Sustainable Groundwater Management: An Interactive Approach

Stream depletion/accretion assessment is critical to developing basin-wide plans for sustainable groundwater management. Groundwater models are commonly used to quantify schedules for stream depletion or accretion from existing groundwater uses, projected changes in groundwater use, or conjunctive use scenarios to meet groundwater management goals. Development of a groundwater model can be a multi-year and expensive process, compounded by the analysis and processing of multiple scenarios and permutations. This process can be streamlined, yielding useful approximations, by simulating a set of baseline actions and using convolution and superposition to explore combinations of actions through an interactive interface. Results, qualified by limitations of linear approaches in non-linear systems, help decision makers understand groundwater dynamics and stream interactions associated with groundwater management actions. This approach is illustrated for the Scott Valley in California.

Hypothetical groundwater management options were analyzed to provide a screening-level comparison of the magnitude and timing of flow increase to the Scott River. Four hypothetical groundwater management options are presented, including delayed groundwater pumping, managed winter recharge, augmentation wells and reduced irrigation pumping. Potential flow benefits are reviewed to understand the scale of the project or projects that may be required to satisfy water rights and to protect aquatic resources. The actions differ notably in the timing of flow benefits. The timing of benefits is a critical factor in judging the suitability of management actions for meeting flow objectives. A graphical comparison of groundwater management flow impacts is facilitated with an interactive spreadsheet-based tool, including user-controlled on/off switches and sliders to select and scale the magnitude of projects. Results may be compared to user-specified monthly flow enhancement targets. The rapid comparison of stream depletion/accretion results, drawing from simulation of selected baseline actions, can provide useful information for stakeholder discussion during the process of developing groundwater sustainability plans.