Description of Pre-Project Hydrology (re: Downstream Flows)

 

Under pre-Project conditions, natural controls existed below both Upper Klamath Lake and Lake Ewauna which stabilized lake levels except during critical droughts.  Those controls were natural reefs of hard earth material in the channel and other channel constrictions.  Under these pre-Project conditions, the Klamath River flowed into Lower Klamath Lake area.  The United States Reclamation Services 1906 map titled “Topographic and Drainage Map, Upper and Lower Klamath Project” shows the invert of the Klamath Strait approximately the same level as the Klamath River channel bottom near Keno.  In addition, the Lost River terminated at Tule Lake .  These flows flooded approximately 183,000 acres within Lower Klamath and Tule Lake .  In general, under pre-Project conditions, Klamath River flows downstream of Keno may have occurred after a certain water level was reached in the Klamath River and Lower Klamath Lake .  The exact timing and frequency of the division of flow between Klamath Straits and the Klamath River is not clear based on historical documents.  

During many dry years under pre-Project conditions, there were times of little or no flow in the Link River below Upper Klamath Lake and Klamath River below Keno.  These conditions occurred as a result of dry runoff conditions and were controlled by the same natural reefs identified above.  During dry years and years of low runoff, evaporation from Upper Klamath Lake likely exceeded the inflow to the lake resulting in little or no outflow.  In addition to these events, high winds from the south periodically kept water from overflowing the natural reefs into the river channels which left certain reaches of the Link River completely dry.  

Under current Project conditions, greater quantities of water can be stored in Upper Klamath Lake for later beneficial use, including agriculture, refuge water, and in-stream flows. The U.S. Bureau of Reclamation is completing it’s draft “Undepleted Natural Flow of the Upper Klamath River”, which concludes that downstream flows in the Klamath River have increased 30 percent over discharges before agricultural settlement occurred. The flow increases are attributed to the fact that irrigated land uses less water than evaporation loss from the swamps and marshes that existed before the shallow lakebeds were reclaimed for agricultural use.   

The Klamath Project changed the timing of flows but has not reduced the overall volume of flow.  The change in timing of flow is discussed above.  A primary component of the difference in volume of water under pre-Project versus post-Project conditions would be the difference in consumptive use within the Lower Klamath and Tule Lake areas.   According to a map of this area during the summer of 1906, approximately 152,000 acres were either marshland or flooded in excess of the current National Wildlife Refuges.   The evaporation from an open body of water in the Tule Lake area during March through October is between 3.0 to 3.5 feet.  This also is a reasonable approximation of the consumptive use of marshland tules and grasses.  Lower Klamath Refuge presently requests 3.5 AF/acre to sustain permanent marshes.  Therefore, the total pre-Project consumption was in the range of 456,000 to 532,000 acre-feet.  Assuming these same lands are all in agricultural production and receiving water, the estimated  consumption is in the 304,000 acre-foot order of magnitude.  This is based on the total evapotranspiration of potatoes at approximately 2.0 AF/Ac which is the highest water using crop behind alfalfa and pasture.  If all of the lands were alfalfa or pasture, we would expect the consumption to be comparable to the lower end of the pre-Project conditions.