Water Resources Research Act Program

Details for Project ID 2013CO290B

Assessing the agronomic feasibility of partial and full season hay fallowing as part of a Western Slope Water Bank

Institute: Colorado
Year Established: 2013 Start Date: 2013-03-01 End Date: 2014-02-28
Total Federal Funds: $20,000 Total Non-Federal Funds: $9,700

Principal Investigators: Joe Brummer

Project Summary: Colorado River Compact compliance in partnership with the other three Upper Basin States is a topic of growing concern within Colorado. Western Slope water users account for about 1.3 million acre feet of Colorado River Basin (CRB) water of which about 1 million are pre-1922 and exempt from Colorado River Compact administration. The populated Front Range diverts about a half-million acre feet of CRB water of which the majority are junior rights to 1922. A possible curtailment scenario is Colorado’s post-1922 water rights forgoing use (or a negotiated fraction) until all of the 75 million acre feet 10-year running average non-depletion requirements to the Lower Division States are restored. A water bank approach might facilitate this arrangement by brokering short-term leases of pre-1922 agricultural rights for temporary use by post-1922 municipal and industrial - mostly Front Range - water right holders. Six irrigated alfalfa or grass hayfield sites will be established in Western Colorado to test fallowing practices likely to be used for generating conserved water for a future water bank. Testing of practices will be side-by-side with a control treatment (i.e. limited or deficit irrigation treatments next to “fully irrigated” or “business-as-usual” irrigation treatments). The test sites will be located throughout the Yampa, Colorado, and Gunnison River basins, an area that includes about 360,000 acres of irrigated grass and/or alfalfa hay. A master’s level graduate student will be recruited in the Soil and Crop Sciences Department at CSU and charged with answering three basic questions about single season hay fallowing in the Upper Colorado River Basin: 1) What is the impact on hay stand life, productivity, and quality due to a single-season fallowing? 2) What is the potential range of marketable, saved (otherwise consumed) water per acre of single-season fully and partially fallowed hayfields in Western Colorado? 3) Are there any environmental benefits or concerns to fallowing hay in Western Colorado? For example, what are the implications for reducing in-stream salt and selenium concentrations in Mancos shale areas? Does fallowing make hayfields prone to weed invasion? Agronomic responses will be determined by measuring yield, species composition, ground cover, and forage quality. Soils will also be sampled and analyzed to assess changes in soil moisture, impacts to soil health, and shifts in salt and selenium on affected sites. Atmometers will be installed at each site to help estimate a range of water savings that might be eligible for leasing through a future water bank. By answering the above three questions, hay producers as well as proponents of water banking will have enough information available to confirm if this approach is worth pursing as a method to free up water to meet compact obligations and/or other uses. There are other questions that must be answered, but if the impacts to yield, forage quality, etc. are too severe or long lasting, then hay producers will be reluctant to participate in a water banking program. Many Colorado CRB water bank discussions focus on legal framework, administration logistics, and return flow effects. This study will not focus on these aspects, only the agronomic implications.