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Alternative Agricultural Water Transfer Methods -Grant Application Form <br />January 2008 <br />measurement, documentation, and engineering needs that will need to be employed in order for the <br />State to administer or monitor these alternatives will be examined. Finally, legal and institutional hurdles <br />and challenges will be described. <br />Long-term Rotational Fallowing <br />Rotaflonal fallowing is a program in which a porflon of the irrigated lands included in the fallowing <br />program are not irrigated in a particular year. For example, an individual irrigated field that is <br />enrolled in the program may be held fallow in one of every four years. The actual frequency of <br />fallowing a particular field depends on the structure of the program. A benefit of long-term <br />rotational fallowing is that water rights can be maintained as productive, appreciating assets that <br />generate revenue as integral components of farming and ranching operations, thereby contributing to <br />economic viability of farm and ranch operations and the vitality of their rural communities. <br />Additionally, the status of the land can remain as irrigated, which benefits both the land owner with <br />respect to land value and the public from a property tax perspective. <br />The State of Colorado has developed tools that are useful in quantifying the consumptive use of <br />various crops and vegetation. StateCU, a consumptive use analysis tool developed by the State of <br />Colorado, will be used to quantify the amount of consumptive use made available in a long-term <br />rotational fallowing program. StateCU will also be used to quantify the on-farm return flows that <br />need to be maintained. The Integrated Decision Support Group at Colorado State University has <br />developed the Alluvial Mater Accounting System (ACAS). This tool will be used to estimate lags <br />associated with the rate at which return flows manifest themselves as streamflow accretions. The <br />tools just described are commonly used in the South Platte River basin for analyses associated with <br />change-of--use cases and augmentation plans. <br />Alternative Cropping <br />Various types of irrigated crops consume different amounts of water. If an agricultural producer <br />historically grew crops that consumed relatively high amounts of water and then switched to irrigated <br />crops that consume less water, the difference in consumption between the older and newer crops <br />could be made available to other water users. This alternative may result in lower economic gains to <br />the producer from the farming operations, but the decrease in economic gains could be mitigated <br />from the sale or lease of the water made available from lower levels of consumption. <br />StateCU will be used to determine the difference in consumption among various crops under <br />different hydrologic conditions. It is possible that return flows will remain the same or even be <br />enhanced under alternaflve cropping scenarios. The degree to which on-farm return flows change <br />will be quantified using StateCU and the impact on streamflows in the South Platte River will be <br />evaluated using ALIAS. <br />Deficit Irrigation <br />Deficit irrigation occurs when the water supplied to a crop is less than what is needed to satisfy the <br />crop's full evapotranspiration needs. The primary impact of deficit irrigation is lower <br />11