Little Applegate Watershed Hydrology Report Michael Zan * Hydrologist April 1995 Little Applegate Watershed Analysis Hydrology Report SECTION 1 LITTLE APPLEGATE RIVER HYDROLOGY Mean Monthly Flows: Except for some data collected from May through October 1913, and from June through October 1994. there is no known flow data for the Little Applegate River or its tributaries. With this in mind it was necessary to construct a hydrograph displaying mean monthly flows by utilizing records from nearby stations that have been published in USGS Surface Water Records and Open-File Reports. In constructing a hydrograph, a short discussion of low flows is first in order. Since low streamflows have been identified as a key question pertaining to the larger issues of water quantity/quality and fish populations, the greatest need is to gain a reasonable estimate of seasonal low flows to help quantify the impacts of water withdrawals on instream beneficial uses. With this in mind, extreme caution must be used when extrapolating data from gaged to ungaged watersheds. This is particularly important in determining low-flow characteristics (Riggs 1972, Gallino 1994 personal communications). The principle terrestrial influence on low flow is geology and the primary meteorological influence is precipitation. Neither have been adequately used to describe effects on low flow using an index so that estimation of low flow characteristics of sites without discharge measurements has met with limited success. Exceptions are on streams in a region with homogeneous geology, topography, and climate, in which it should be possible to define a range of flow per square mile for a given recurrence interval. Again according to Riggs (1972), although estimates of low flow characteristics from basin characteristics are generally of low accuracy, the desire to estimate such characteristics for an ungaged watershed may justify development of regional relationships where conditions are favorable; namely that if all significant basin characteristics except drainage area in a region have extremely limited ranges, one would expect a good relation between low flow characteristics and drainage area. Unfortunately, the gaged watersheds in southwestern Oregon in the vicinity of the Little Applegate River represent a wide range of geologic as well as meteorological characteristics. With this in mind, the records and watershed characteristics for the nearest gages which might be useful for extrapolating flows for the Little Applegate have been examined. These gages/watersheds are: Elliot Creek (USGS #14361600 - 51.8 sq mi - 10 years data), Middle Fork Applegate River (USGS #14361590 - 50.7 sq mi - 8 years data), Carberry Creek (USGS #14361700 - 68.9 sq mi - 10 years data), and Applegate River near Copper (IJSGS #14362000 - 225 sq mi - 41 years data). None of these streams were regulated for their periods of record, except for some minor winter storage at Squaw Lakes Reservoir and some minor diversions on upper Carberry Creek. Elliot Creek is geologically distinctly different from the other gaged watersheds (and the Little Applegate) except that it is included in the larger watershed represented by the gage on the Applegate River near Copper. Elliot Creek is almost entirely underlain by schist parent material. Carberry Creek and the Middle Fork Applegate are similar to the Little Applegate Watershed in that they are underlain primarily by metasedimentary and metavolcanic rocks of the Applegate group; they all also have significant acreages in granitics. The watershed area above the Applegate River gage near Copper Page 2 Little Applegate Watershed Analysis Hydrology Report includes Carberry Creek, the Middle Fork Applegate. Elliot Creek. Squaw Creek and several minor facing streams. Portions of Squaw Creek and all of the facing streams are geologically similar to Carberrv Creek. the Middle Fork Applegate, and the Little Applegate. Because of the ob%ious differences in geology, the Elliot Creek data was not used. Although the Middle Fork Applegate is geologically similar to the Little Applegate. the weighted average annual precipitation for the watershed is substantially higher: it averages about 55 inches per year in the Middle Fork drainage verses 38 inches in the Little Applegate. For this reason the Middle Fork data was not used. The geology and precipitation patterns of the watersheds tributary to the Carberry Creek and Copper gages were next compared to those features of the Little Applegate River Watershed. Geologically. Elliot Creek and a portion of Squaw Creek in schist parent material comprise about 25 percent of the watershed area above the Copper gage. The flows at this gage would thus appear to be most heavily influenced by the 75 percent of the Watershed that is in metasediments and metavolcanics. Regarding precipitation. Carberry Creek watershed receives a weighted average of 45 inches of precipitation per year and the Applegate River Watershed above Copper receives about 42 inches per year. compared to the Little Applegate's 38 inches. Approximately 22 percent, 27 percent. and 17 percent of the Carberry, Applegate at Copper, and Little Applegate River Watershed areas. respectively, are in the zone above 5000 feet elevation dominated by snow. The corresponding percentages of those watersheds in the 4000-5000 foot transient snow zone are 33 percent. 30 percent. and 16 percent. respectively. The respective percentages in the zone below 4000 feet that is dominated by rain are 45 percent, 43 percent, and 67 percent. From this it appears that the distributions of types of precipitation are similar above the Carberry and Copper gages, both of which have proportionally more area in the snow and transient snow zone than found in the Little Applegate River Watershed. In this regard neither site has an advantage. Based on both geologic and climatic factors. it was felt that data from either of these stations would be useful in determining an estimate of mean monthly flows in the Little Applegate. A comparison of normalized mean monthly flows displayed as CSM (cubic feet per second per square mile) was made between the two stations as summarized in Table #1. The numbers display a remarkable similarly between the two sets of data., particularly during the critical low flow period from July through October. Since there are 41 years of data (1939-80) for the Applegate River gage near Copper, verses only 10 years (1977-87) for the Carberry Creek gage, the (CSM) data from the gage near Copper was selected to construct a hydrograph to represent the Little Applegate River flows at its mouth. The close similarity in geology and climate suggested that an adjustment factor was not needed; that is. a direct application of Applegate at Copper CSM data to the Little Applegate was deemed appropriate. The hydrograph (see Figure # 1) displays mean monthly flow in cubic feet per second (cfs). Page 3 I Little Applegate Watershed Analysis Hydrology Report Table #1 Little Applegate River Mean Monthly Flow CFS per Square Mile (CSM) Carberry Applegate River Creek near Cooper January 3 40 3 76 February 5.07 3 44 March 4 00 2.99 April 3.44 3.23 May 2.91 3.33 June 1.35 1.65 July 0.46 0.52 August 0.24 0.26 September 0.24 0.22 October 0.40 0.44 November 1.67 1.27 December 3.72 2.66 Figure #1 Estimated Mean Moathly Flow(cfs) at Mouth of Little Applegate River 450 400 350 ____ __' 300 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 250 _ __ _ Cfs 200 100 50 0 Jant Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec It is emphasized that this is only an approximation of long term mean monthly flows. It is considered reasonably close to natural, unaltered flows for purposes of this analysis. Although no adjustment factor was used, these values, particularly low summer flows, may be slightly liberal since the Little Applegate receives about 90 percent of the average precipitation received in the watershed abo e the gage at Copper, and since a greater percentage of the watershed above Copper lies within the predominantly snowfall zone above 5000 feet (27% verses 17%) which suggests greater dela\ ed surface and subsurface flows. In reality, although there are no storage facilities in the Little Applegate Page 4 Little Applegate Watershed Analysis Hvdrology Report Watershed, there are numerous diversions which affect the amount of strearnflow during the April through October irrigation season. This will be addressed in the following subsection on low flows. The hydrograph (Figure #1) displays a pattern of natural runoff that is common to streams in the Siskivou Mountain Range of the Klamath Mountain Physiographic Province. It is reflective of the Mediterranean climate of Southern Oregon. High mean monthly streamflows parallel the wet winter and spring months followed by a prolonged period of low flows during the droughty summer and early autumn. Figure #2 displays the pattern of annual distribution of precipitation in this region. Onlk about six percent of the annual runoff in the Little Applegate Watershed normally occurs from July through October; about 15 percent of annual precipitation occurs during the same four-month period (half of this coming in October). Figure #2 Mean Monthly Precipitation (inches) at Buncom (NOAA Sta Index No. 1149) 4.5 4.0 3.5 3.0 *2.5 c~2.0 1.5 1 .0 0.5 0.0 1`1 -1 -, U .1 q1 ~ j 0 z Cs No attempt has been made to quantify the contributions of individual subwatersheds to the total flow within the Little Applegate Watershed. By observation though, it is obvious that the major contributing streams are McDonald Creek, Glade Creek, and Yale Creek. Other important sources are Split Rock Creek, Bear Gulch, Lake Creek, and Greeley Creek. Background Low Flows and Human Processes Affecting Those Flows: As previously mentioned, extremely low streamflows (due to water withdrawals) has long been identified as a concern contributing to the larger issues of water quantity/quality and fish populations.