Precipitation as rainfall averages 41-42" annually, precipitation as snowfall is 12-13" annually, and runoff averages 12" annually (MDNR 1986). The highest runoff is in April-May and the lowest in September, coinciding with seasonal rainfall patterns. Winter snowfall contributes minimally to runoff in the basin, which is primarily rainfall driven (MCWC 1974).
The longest running active gauging station in the basin is station 07189000 on the Elk River near Tiff City, Missouri. This gauge records data from a drainage of 872 square miles. It has been in use from October 1939 to present (USGS 1998). Several other gauges have been intermittently used on streams in the basin. Gauge 07188850 on the Elk River at Pineville (1942, 1945, 1947, 1949, 1952, 1962-1965, 1967), gauge 07188870 on Indian Creek at Anderson (1942, 1945, 1947, 1949, 1952, 1962-1965, 1967), gauge 07189100 on Buffalo Creek at Tiff City (1954, 1962-1964, 1967-1975, discontinued partial record station), and gauge 07188500 on Lost Creek at Seneca (1949-1959, 1967-1975; drainage area 42 sq. mi.). Other gauging stations that have been used in the Elk River basin are gauge 07188820 on Little Sugar Creek at Caverna (1967-1975), gauge 07188660 on Mikes Creek at Powell (5/94-5/95), and gauge 07188855 on North Indian Creek near Wanda (5/94-5/95). Groundwater levels were monitored using wells at Longview (1984-1991) and Noel (1984-1991).
Funk (1968) listed the Elk River basin as having 169 miles of permanently flowing and 17 miles of intermittently flowing streams with permanent pools in Missouri. The MDNR reported that the Elk River basin in Missouri had 160 miles of classified streams (151 miles of permanently flowing stream, and 9 miles of intermittently flowing streams with permanent pools) (MDNR 1985).
There are 234 third order and larger streams in the Elk River basin with a total stream mileage of 1,115 miles (Table Hy01). The permanence/ intermittence of streams usually can be determined from 7.5 minute series topographical maps. Permanent streams are indicated with solid blue lines, and intermittent streams are indicated with dashed blue lines. As of June 1999, several of the topographical maps covering the Elk River basin are only available as provisional editions (draft maps). These provisional maps have all rivers shown as black dashed lines making permanence/intermittence determinations very difficult for many streams. In visiting with personnel of the USGS it was learned that these maps will probably remain provisional maps unless demand increases or some entity comes forward with funding to finish them. Figure Hy01 displays the topographical maps covering the basin. Losing streams are widespread in the Elk River basin. A losing stream is one where water is "lost," usually into the streambed and becomes groundwater rather than surface water. Losing stream reaches in the Elk River basin are listed in Table Hy02.
Stream Flow/7-Day Q2 and Q10 Low Flow
On average, in the Missouri portion of the watershed, an area of 5.03 square miles is required to maintain one mile of permanently flowing stream (MDNR 1986). The highest average flows are in April-May, and the lowest are for September, coinciding with the pattern of precipitation which is highest in the spring and lowest in the fall (Figure Hy02). The highest estimated flow in the Elk River was April 19, 1941, when 137,000 cubic feet per second (cfs) was reported near Tiff City (USGS 1998). The lowest recorded flow at this gauging station (07189000) was 5.1 cfs on September 5, 1954 (USGS 1998). Average flow at this station is 835 cfs (USGS 1999a). There is concern about reduced flows from Arkansas into the Missouri portion of the watershed. Decreased flows have the potential to negatively affect water quality and aquatic life in the watershed (Lobb 1998).
Low flows for streams in the Elk River basin are listed in Table Hy03. The 7-day Q2 is the minimum flow expected for a seven day period that will occur on average once in two years. The 7-day Q10 is the minimum flow expected for a seven day period that will occur on average once in ten years. The lowest flows usually occur in the late summer and fall (August, September, and October). Flows tend to be sustained through dry periods by springs and groundwater. Flow duration curves (Figures Hy03 and Hy04) indicate the tendency of stream flow to vary over time. Flows are variable for the Elk River basin, but the ready infiltration of surface water into the groundwater system reduces the magnitude of high flows. The corollary discharge of groundwater during dry periods tends to maintain stream flow. This exchange between groundwater and surface water tends to moderate and maintain more "normal" flows in all but extreme conditions.
Dam and Hydropower Influences
There are no major dams in the Missouri portion of the basin. The lower Elk River is inundated in Oklahoma by Grand Lake O’ the Cherokees (an impoundment on the Grand [Neosho] River). There are several small to moderate-sized public and private lakes in the basin (Table Hy04). Due to the soil types and bedrock in the basin, farm ponds are not as numerous as in many other parts of Missouri. Most ponds can be built without permits, and statistics on ponds are usually compiled by county rather than watershed. These factors complicate the acquisition of accurate, up-to-date information on ponds. Concern exists over the effects ponds have on low-flow conditions as they intercept runoff and allow little or no adjustment for maintenance of stream flows. Gordon (1980) reported three small dams on major tributaries and rivers in the Elk River basin. Indian Creek was impounded at McNatt, Missouri, the Elk River at Noel, Missouri, and Little Sugar Creek at Bella Vista, Arkansas. Based on USGS maps that were photo revised in 1982, there were six new impoundments on tributaries of Little Sugar Creek and one new impoundment on Little Sugar Creek in the Bella Vista area. Flows and water quality in the Little Sugar Creek sub-basin could be altered due to these new impoundments.