Average annual precipitation for the Crooked River basin ranges from 36 to 38 inches (Vandike 1995). Average annual runoff is about 8.5 inches (Vandike 1995). Seventy percent of the rainfall occurs during the growing season (Preston 1986). Annual snowfall is about 20 inches (MDNR 1986a) with about 30 days of continuous snow cover (Detroy and Skelton 1983).
The two gauging stations in the Crooked River basin are both located near Richmond, Missouri. The gauge on the mainstem Crooked River (number 06895000; in operation from 1948 through 1970) was a continuous-record streamflow gauging station, located at the Highway 13 bridge, 4 miles north of Richmond and records data for a drainage area of 159 square miles. The other gauge (number 06895050; a low-flow station) located on the West Fork Crooked River at Richmond recorded data in 1943, 1945, 1946, 1953, and 1962 (Detroy and Skelton 1983).
Permanent and Intermittent Streams
The mainstem Crooked River was classified as permanently flowing for 30 miles and intermittently flowing for 30 miles in 1968. Estimates for the Crooked River basin, including the East and West Fork Crooked rivers, were 47 miles of permanent flowing and about 35 miles of intermittent flowing streams (Funk 1968).
There are 59 third order and larger streams in the Crooked River basin with a total stream mileage of 371 miles (Table Hy01). The permanence/intermittence of particular streams can be determined from 7.5 minute series topographical maps found in the coverage in Table Hy01. Permanent streams are indicated with solid blue lines and intermittent streams are indicated with dashed blue lines. Based on current USGS 7.5 minute maps there are 177 miles of permanently flowing and 50 miles of intermittently flowing streams and rivers, fourth order or higher, in the Crooked River basin. Most third order and lower streams in the basin are intermittent. Increased intermittence resulting from lower base flows and sedimentation is occurring throughout the basin. Crooked River basin streams suffer from poor baseflows due to the relatively impermeable nature of basin soils (MDNR 1986b).
Average annual discharge for the gauging station on the mainstem Crooked River was about 99 cubic feet per second (DuCharme and Miller 1996). Lowest discharge usually occurs
midwinter and highest discharge in the summer months (Figure Hy01). The highest recorded flow was 29,000 cubic feet per second on July 20, 1965 (Vandike 1995). Periods of no flow have occurred in the Crooked River (Vandike 1995).
7 Day Q2 and Q10 Low Flows
Streams in the Dissected Till Plains Region, including the Crooked River, have poor low flow potentials due to low hydraulic conductivity of area soils and poor land use practices. Low flows in the basin usually occur in the months of August, September and October (Skelton 1976). Low flow characteristics can usually be generalized in plains streams based upon the size of the drainage area. Streams with basin areas less than 100 mi2 will almost always have 7-day average minimum flows at recurrence intervals of two years (7-day Q2) of zero. About 60 percent of plains streams with drainage areas of 100 to 200 mi2 will have 7-day Q2 of zero and the remainder will have 7-day Q2 of 0.1 to 1.0 cfs. This method is unreliable for basins with drainage areas larger than 200 mi2, and field observations are required. The 7-day average minimum flows at 10 year intervals (7-day Q10) for drainage basins of 200 mi2 or less are almost always zero. About 70 percent of plains streams with drainage areas of 200 to 1,000 mi2 will have 7-day Q10 of zero and the remainder will have 7-day Q10 of 0.1 to 1.5 cfs (Skelton 1976). Lowest mean discharge in the Crooked River for 7 days consecutively is zero (Skelton et al. 1982). The 7 day Q2 is 0.2 and 7 day Q10 is zero (MDNR 1995). The flow duration curve (Figure Hy02) indicates the Crooked River basin has highly variable flows. Basin streams tend to rise and subside swiftly in response to precipitation events.
Dam and Hydropower Influences
There are no major dams in the basin. There are a few small public and private lakes and a large number of farm ponds in the Crooked River basin. In the early 1980's it was estimated that Ray County contained 3,500 small impoundments (Preston 1986). Due to small size and ease of construction, the number of ponds can change very rapidly. Many ponds are built without needing permits and statistics on ponds are usually compiled by county rather than watershed. These factors complicate getting accurate, up-to-date information on ponds. Concern exists over the effects these ponds have on low-flow conditions as they intercept runoff and allow little or no adjustment for maintenance of stream flows.