State v. State

Background

This text comes from a court decree (a formal court order) that includes an appendix of accounting procedures about interstate water. The parties are States that share a river basin and the RRCA, which provides a groundwater model. The appendix explains how to count Imported Water Supply Credits, mentioning Nebraska’s Imported Water Supply and specific modeling steps taken from the August 12, 2010, Accounting Procedures.

Reasoning

The core practical question is how to measure and credit water that one State imports into the shared basin. The court’s order uses the RRCA Groundwater Model to make this measurement. For imported-credit calculations, the model runs two scenarios: a "base" run with all pumping and recharge active, and a "no NE import" run that turns off surface water recharge tied to Nebraska’s imported supply. The Imported Water Supply Credit equals the difference in stream flows between these two runs. The appendix also explains how to compute each State’s groundwater consumptive use by comparing a "base no NE import" run with a "no-State-pumping" run and by measuring baseflow changes at defined stream locations.

Real world impact

Practically, these rules tell basin managers and state water agencies exactly how to claim and count imported water credits and how to measure streamflow depletions from pumping. The appendix specifies that values are tallied by sub-basin and for main-stem reaches above and below Guide Rock. The court also says it will retain jurisdiction to enforce, modify, or issue further orders to give the decree effect, so these procedures may be adjusted later if needed.