Modelling of Instream Benefits from Flow Improvements Through Real Time Water Management in the Shasta River, California

The Nature Conservancy (TNC) recently acquired two adjacent cattle ranches to help restore salmon populations in the Shasta River, a critical tributary for Klamath River salmon. These properties encompass 6,238 acres, include 19 cubic feet/second water rights to cold spring sources, and take in more than 10 miles of prime salmon spawning and rearing habitat. Our primary objectives with these acquisitions are to: 1) implement significant stream restoration and 2) develop and promote solutions to stewardship-related problems associated with irrigated agriculture that have contributed to the decline of salmon populations.

As we developed this restoration project we assumed: 1) the threats associated with irrigated agriculture must be abated if we are to meet long-term conservation goals for salmon and other freshwater species; 2) irrigators in the Shasta Basin, and throughout the West, can reduce the amount and improve the timing of their water application to help meet fisheries restoration objectives, 3) lack of information is limiting on-the-ground management decisions, therefore improving data collection to guide irrigation practices will benefit salmon spawning and rearing habitat by improving water flows and temperatures in key sections of the Shasta River and its tributaries; and 4) landowners will be motivated by economics and regulatory pressure to adopt new irrigation methods.

As part of this restoration work, Watercourse Engineering, Inc. (WE) developed a two-dimensional flow and temperature model of Big Springs Creek that is a valuable tool to restoration planning and water management decision making. This model has assessed a wide range of restoration prescriptions, including channel modifications, shading features, flow operations, and irrigation return flow management/control. 

Using information gleaned from this model, TNC and WE incorporated the use of real-time flow, water temperature and land management data collection in order to develop an adaptive irrigation and ranch management plan that manages for dual purposes: ranch goals such as pasture growth, and ecological goals such as cold water refugia for rearing coho salmon. Coupling model simulation information with technologies such as remote sensor arrays, soil moisture meters, and automated irrigation systems, we have facilitated real-time decision making by on-site and off-site managers regarding diversion amount and timing, pasture rotation, and management of discharges, or tailwater releases, to the Shasta River and its tributaries. Working to export these methods to other ranches, TNC is exploring opportunities to incorporate economic incentives, such as water rights purchase and leasing, into this effort.