Geology and Geomorphology
Geology and Geomorphology
The Current River Watershed occurs primarily within the Ozarks Soil Region. Allgood and Persinger (1979) describe the Ozark Soils Region as "cherty limestone ridges that break sharply to steep side slopes of narrow valleys. Loess occurs in a thin mantle or is absent. Soils formed in the residuum from cherty limestone or dolomite range from deep to shallow and contain a high percentage of chert in most places. Some of the soils formed in a thin mantle of loess are on the ridges and have fragipans, which restrict root penetration. Soil mostly formed under forest vegetation with native, mid-tall and tall grasses common in open or glade area."
The following is a list of Ozark soil associations found in the Current River Watershed:
•Captina-Clarksville-Doniphan: "Nearly level to very steep, moderately well drained to excessively drained loamy upland soils that have fragipans or soils that are cherty throughout." (Allgood and Persinger 1979)
•Captina-Macedonia-Clarksville: "Nearly level to very steep, moderately well drained to somewhat excessively drained, loamy upland soils that have fragipans or soils that are cherty throughout." (Allgood and Persinger 1979)
•Captina-Macedonia-Doniphan-Poynor: "Nearly level to very steep well drained and moderately well drained, loamy upland soils that have fragipans or soils that are cherty throughout." (Allgood and Persinger 1979)
•Hartville-Ashton-Cedar Gap-Nolin: "Deep, nearly level to gently sloping, somewhat poorly drained to excessively drained, loamy bottom land soils." (Allgood and Persinger 1979)
•Hobson-Coulstone-Clarksville: "Gently sloping to very steep, moderately well drained to somewhat excessively drained, loamy soils with fragipans or soils that are cherty throughout."(Allgood and Persinger 1979)
•Lebanon-Hobson-Clarksville: "Gently sloping to very steep, moderately well drained to somewhat excessively drained, loamy and clayey soils with fragipans or soils that are cherty throughout." (Allgood and Persinger 1979)
•Loring-Union-Doniphan: "Nearly level to very steep, well drained and moderately well drained, loamy upland soils that have cherty subsoils or fragipans." (Allgood and Persinger 1979)
•Wilderness-Clarksville-Coulstone: "Gently sloping to very steep, moderately well drained to excessively drained, loamy upland soils that have cherty subsoils or fragipans." (Allgood and Persinger 1979)
A small portion of the Current River Watershed in southeastern Ripley and southwestern Butler Counties occurs in the Mississippi Delta Soils Region. Allgood and Persinger (1979) describe the soils of this region:
"These soils are in the broad, nearly level flood plains and low terraces of the Mississippi River and associated tributaries. Crowley's Ridge is the major sloping landform in the region. The upland loess mantle of the ridge is underlain by loamy, sandy, or gravelly deposits. Soils are deep on the flood plains, formed in loamy, sandy, and clayey alluvium. On the ridge soils are deep, loamy, or sandy. Some areas have fragipans. These soils of the lowlands formed under vegetation consisting of wetland, grasses, forest, sedges, and shrubs."
The following is a list of Mississippi Delta soil associations found in the Current River Watershed:
•Calhoun-Amagon: "Deep, nearly level to gently sloping, poorly drained loamy soils on slightly concave stream terraces." (Allgood and Persinger 1979)
•Bosket-Tuckerman: "Deep, nearly level to moderately sloping, well drained to poorly drained, loamy soils on stream terraces." (Allgood and Persinger 1979)
Geology and Karst
The geology of the Current River Watershed consists primarily of dolomites and sandstone/dolomites of Ordovician age (Figure Ge01). A significant exposure of Cambrian Dolomite is present in the middle portion of the watershed. This is mainly associated with major stream valleys. Exposures of Precambrian Igneous Rock are also present in the middle portion of the watershed. Both the Cambrian dolomite and Precambrian igneous rock are geologic exposures associated with the St. Francois Uplift. Within the Current River Watershed, the effects of the uplift are most pronounced in the middle portion of the watershed. As a result, the rocks in this portion of the watershed are older than in other areas of the watershed. Quaternary Alluvium, associated with the Bootheel area of Missouri, exists in the southeastern portion of the watershed on the southeastern side of the Little Black River. In, addition a few small areas of Mississippian limestone and limestone/sandstone occur on the watersheds eastern boundary.
As is the case in most watersheds of the Ozarks, the geology of the Current River Watershed (primarily consisting of soluble rock formations of dolomites and sandstone dolomites), in combination with an average annual precipitation of over 40 inches has created a karst landscape within the watershed. This karst landscape is characterized, in part, by a close relationship between the surface water and groundwater systems. Within karst landscapes, points or areas of surface water/ground water interaction include losing streams, sinkholes, and springs.
Losing streams are one manner in which surface water is transported or "lost" to the groundwater system. Within the Current River Watershed, 211 miles of streams have been designated as "losing" in the Rules of Department of Natural Resources Division 20-Clean Water Commission Chapter 7-Water Quality (Table Ge01 and Figure Ge02) (MDNR 2000c). This is estimated at 1 mile of losing stream to 12.5 square miles of watershed area (1:12.5). This is a higher concentration of losing streams than has been documented within the Jacks Fork which has a ratio of 1 mile of losing streams to 50 square miles of watershed area. However, this is a relatively lower figure in comparison to the North Fork and Eleven Point Watersheds which have losing stream densities of 1:7.7 and 1:4.2 respectively. Within MDNR 2000c, a losing stream is defined as "A stream which distributes 30% or more of its flow during low flow conditions through natural processes, such as through permeable geologic materials into a bedrock aquifer within two (2) miles flow distance downstream of an existing or proposed discharge". Due to the specific nature of this definition, many streams within the watershed, which possibly lose large amounts of flow to the groundwater system, may have yet to be surveyed or classified as being "losing" in the broader sense of the word. Further study may be needed in order to develop a comprehensive understanding of the role of losing streams within the watershed.
In addition to losing streams, sinkholes provide another point of surface to groundwater interaction. While sinkholes are known to be common in the region surrounding the Current River Watershed, detailed information regarding sinkhole location and/or densities is limited. In order to better understand the extent of occurrence of sinkholes additional research is needed.
Several dye traces have been performed within the Current River Watershed by public and private agencies (Figure Ge02) (MDNR 2000a). Dye traces are useful for determining ground water movement and spring recharge area. Dye trace data for the Current River Watershed indicates that the watershed receives substantial amounts of ground water from neighboring watersheds including the Jacks Fork, Meremac, Black, and the Eleven Point. The most notable and well defined area of ground water transport is within the Big Spring recharge area. Much of the Big Spring recharge area occurs within the Eleven Point River Watershed where the longest dye trace was found originating in the Middle Fork, a strait line distance of 39 miles. There is little evidence of substantial groundwater transport from the Current River Watershed to neighboring watersheds. The exception to this is a trace completed from a sinkhole within the watershed which was recovered at Alley Spring in the Jacks Fork Watershed.
Springs are the naturally occurring outlets of groundwater systems. Spring flow accounts, to a large extent, for the higher sustained flows of many Ozark streams, including the Current River, relative to streams in other regions of Missouri. Within the watershed there are 248 known springs (1 spring /8.3 square miles of watershed area) (MDNR 2000b) (Figure Ge01). Vineyard and Feder (1974) list discharges for 49 springs within the watershed (Table Ge02). Twenty six of these springs have discharges exceeding 1 cubic foot per second (cfs). The largest spring within the watershed is Big Spring which has an average flow of approximately 428 cfs. This flow rate makes Big Spring the largest spring within the Ozarks Region of Missouri and Arkansas.
Stream Order, Mileage and Permanency
Stream order is "a hierarchy in which stream segments are arranged" (Judson et al. 1987)
The process of stream ordering is accomplished by examining maps and assigning orders to stream segments based on other streams which flow into them. When two stream segments of the same order join, the new segment they create is the next highest order. For instance, a first order stream would be a stream in which no other streams intersect it. A second order stream is created by the joining of two first order streams. A third order stream is created by the joining of two second order streams and so on. If the main channel of a stream happens to be a lower order than that of the intersecting stream, the main channel assumes the higher order. If the main channel is a higher order stream than the intersecting stream, it maintains the higher order (Figure Ge03). Two types of order are discussed within this document: Horton order which is the maximum order of a stream at its mouth; and Strahler order which is the immediate order of a stream at any given segment of its length. For instance the Strahler order of No Name Creek at point A in Figure Ge03 is second order while the Horton Order for the main channel designated as No Name Creek is third order.
Horton orders for streams within the Current Watershed have been obtained from a 1:24,000 scale Geographic Information System (GIS) hydrography coverage. There are 197 third order and larger streams within the watershed (Table Ge03 and Figures Ge04, Ge05 and Ge06). These streams account for a total of approximately 1,646 stream miles or 30% of the total stream miles within the watershed. Of the 197 third order and larger streams within the watershed, 157 are third order (857.8 miles), 30 are fourth order (351.3 miles), 8 are fifth order (164.3 miles), and 2 are sixth order (95.5 miles). The Current River is 177.3 miles long and becomes seventh order at the confluence of the Jacks Fork River.
Stream mileage per order (Strahler) for the Current River Watershed has been obtained from a 1:24,000 scale Geographic Information System (GIS) hydrography coverage. Of a total of 5,285 miles of stream within the watershed, approximately 3,255 miles (62%) are first order segments; 920 miles (17%) are second order; 490 miles (9%) are third order; 326 miles (6%) are fourth order; 128 miles (2%) are fifth order; 31 miles (<1%) are sixth order; and 135 (3%) are seventh order. Table Ge04 lists length by order for fourth order and larger streams within the Current River Watershed.
Permanent stream mileage data based on the 1:24,000 National Hydrography Dataset (NHD) for the Current River Watershed indicates that approximately 678 stream miles (13%) within the watershed have permanent water. This equals approximately 1 mile of permanent stream for every 3.9 square miles of drainage area. Lengths of permanent stream by Strahler Order are as follows: first order-28 miles (<1% of all first order miles are permanent); second order-63 miles (7)%; third order-150 miles (31%); fourth order-213 miles (65%); fifth order- 74 miles (58%); sixth order-30 miles (97%); and seventh order-87 miles (100%).
It is important to note that permanent stream mileage data within the 1:24000 NHD is based on USGS Digital Line Graph hydrography data which, in turn is based upon USGS 1:24,000 scale topographic maps (USGS 1998e, USGS 1999b, MoRAP 2002). The USGS assigns a stream permanent status based on that stream having flow twelve months out of the year during normal precipitation (Weirich 1993, Blanc etal. 1999). This method may not take into account periods of drought or the possible "losing" nature of a stream.
Total drainage area of the Current River Watershed is River Watershed is 2,621 square miles (1,677,440 acres). The drainage area of the watershed in Missouri (not including the Jacks Fork Drainage) is 2069 square miles (1,324,424 acres). In order to facilitate analysis of watershed characteristics the watershed was divided based on eleven digit hydrologic units. This resulted in 8 units (Figure Ge07). The largest of these units is the Little Black River unit which drains approximately 382.2 square miles (244,582 acres).
Stream Channel Gradient
Channel gradient was determined for all fourth order and larger streams within the Current River Watershed using data digitized from USGS 7.5 minute topographic maps. Composite gradient graphs were constructed for all fifth order and larger streams within the watershed (Figures Ge08, Ge09, Ge10, Ge11, Ge12, Ge13, Ge14, and Ge15). Average gradients for fourth order and larger streams within the watershed rangefrom 1.2 feet per mile to 84.5 feet per mile. The Current River has an average gradient of 3.9 feet/mile.