Description of Klamath Project Efficiency  

Davids Engineering prepared a draft report in October of 1998 for the Bureau of Reclamation titled “Klamath Project Historical Water Use Analysis.”  This report is based on water use data beginning in October of 1961 and ending in September of 1997.  The following is a quote of Section 5.4, discussion of Project efficiency, from the report.  

The results of this study indicate that the effectiveness of water use in the Klamath Basin depends greatly on how the system is analyzed.  If the analysis assumes a frame of reference that encompasses a portion of the Project viewed over a short period of time, the results are highly variable.  For example, a snapshot focused on early season irrigation applications in upstream subregions reveals low classical efficiencies, whereas, a snapshot of downstream subregions taken during peak use months indicates high efficiencies.  By contrast, if Project operations are viewed from a perspective that combines subregions, a much more uniform picture emerges revealing consistently high classical efficiencies.  The conclusion that historical operation of the Klamath Project has been effective is reinforced by analysis of the Project’s effective efficiency.

An implication of the variability evident in the month to month snapshots of classical efficiencies is that there are important temporal and spatial interactions within the Klamath Project.  For example, these snapshots suggest that the runoff of diverted water that reduces efficiencies in upstream subregions leads to increased efficiencies in Subregion 3 where some of the upstream diversions are ultimately consumed.  A consequence of this observation is that a program intended to improve efficiencies by reducing return flows in Subregions 1 and 2 could have a negative effect on the classical efficiency of Subregion 3 and have little net effect on the efficiency of the Project as a whole. 

Analysis of the monthly patterns of classical efficiencies, both for individual subregions and for combined subregions, indicates that early season irrigation efficiencies are typically low while efficiencies during the peak use months of July and August are very high.  This pattern demonstrates how the classical formula penalizes root zone replenishment as diverted water that is not immediately consumed.  However, the root zone replenishment that is penalized early in the season leads to the very high efficiencies during the peak demand period when soil moisture is consumed.  This peak period withdrawal of soil moisture frequently leads to instances when consumption in July and August is greater than reported diversions and classical efficiencies are computed to be greater than 100 percent.

The above observation implies that a sophisticated seasonal pattern of water use has evolved in the Klamath Project.  Early in the irrigation season the Project’s diversion and conveyance capacity is used to distribute water to meet immediate irrigation requirements and to replenish soil moisture throughout the Project area.  Later, soil moisture stored in the first months of the irrigation season allows the Project to meet peak consumptive use demands even when these demands exceed the Project’s capacity to divert and deliver surface water.

This perspective illustrates a relation between operational practices early in the irrigation season and the Project’s ability to respond to peak period demands.  In particular, this suggests that  reduction of irrigation deliveries during April and May could yield unintended consequences that might not be apparent until two months later.

In summary, should hydrologic conditions make adjustments in irrigation diversions necessary to follow the annual operations plan, decision makers should base allocation decisions on the understanding that the Klamath Project has developed into a highly effective, highly interconnected form of water management.  As a result, careful consideration should be given to implementing operational changes that meet their objectives without setting in motion a chain of unintended consequences that negate the benefits of the modified operations.   

The subregions identified in the above quote are described in general as follows: