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Station (m) 0 50 100 150 200 250 300 Elevation (m) 25.5 26.0 26.5 27.0 27.5 28.0 28.5 29.0 June 2015 July 2014 Distance(m) 0 5 10 15 20 25 Elevation (m) 437 438 439 440 441 442 443 River Kilometer 0 2 4 6 8 10 12 Thalweg Elevation (m) 420 425 430 435 440 445 450 Intial Thalweg Profile Predicted Thalweg Profile Location W1L1 W2L1 W3L3 W3L2 W3L1 W4L1 W4L2 F2L1 F2L2 F2L3 F3L1 Critical Shear Stress, c (Pa) 0 2 4 6 8 10 12 14 Erodibility Coefficient, k d (cm 3 N -1 s -1 ) 0 100 200 300 400 500 600 c k d Critical Shear Stress, c (Pa) 1 10 100 Willow Fivemile Critical Shear Stress, c (Pa) 0.01 0.1 1 10 Fivemile Willow Typically conservation practices aimed at minimizing sediment loading to streams and reservoirs have focused on upland and riparian erosion control and sediment transport reduction. However, in many watersheds, significant sediment loads originate from streambanks and channels currently in disequilibrium. Channel and riparian conservation practices can be implemented to reduce this sediment in conjunction with upland practices, but little knowledge exists on prioritizing locations and evaluating performance of integrated upland, riparian, and in-stream practices. This research hypothesizes that watershed-scale biophysical research, socioeconomic research, and outreach activities can effectively identify and encourage implementation of the most cost-effective and ecologically-beneficial combination of upland, riparian, and in-stream practices to reduce sediment loads and improve water quality, thereby conserving resources to meet potentially altered water availability and demand. Research, education, and extension activities will be focused in the Fort Cobb watershed, located in southwest Oklahoma, but generalizable to other watersheds, especially those throughout the Great Plains. Research includes process-based modeling of upland and channel erosion with and without conservation practices under various land management and climate scenarios. Preferences of adjacent landowners, policymakers, and citizens are beginning to be surveyed in order to prioritize potential stabilization schemes and determine benefits from upland and/or in-stream sediment control. The extension program has started to involve stakeholders, including the Caddo Nation, and educate landowners, natural-resource managers, policy makers, and youth about integrated upland, riparian, and in-stream practices to reduce stream sediment loads. Introduction Implementation of In-Stream, Streambank and Riparian Practices in Conjunction with Upland Practices for Conservation of Water Resources G.A. Fox 1 , H. Enlow 1 , K. Klavon 1 , D.E. Storm 1 , J. Vogel 1 , T. Boyer 2 , L. Sanders 2 , A. Stoecker 2 , P. Starks 3 , D. Moriasi 3 , J. Steiner 3 1 Department of Biosystems and Agricultural Engineering, Oklahoma State University, Stillwater, OK 2 Agricultural Economics, Oklahoma State University, Stillwater, OK 3 USDA-ARS Grazinglands Research Laboratory, El Reno, OK Acknowledgements Landowner Surveys Background and Hypotheses • Upland conservation practices have been implemented in the Fort Cobb Reservoir watershed in recent years: • No-tillage management, conversion of cropland to grassland, cattle exclusion from streams, and various structural and water management practices • Concerns about sedimentation of the reservoir persist due to the fact that a majority of the sediment load is believed to originate from streambanks and channels: • Rapid geomorphic assessment (RGA) indicated that unstable stream channels dominated the stream networks [but also identifying reaches in relatively stable condition. • Using 7 Be and 210 Pb as radionuclide tracers, analysis of one high rainfall intensity storm event indicated that as much as 50% of suspended sediment was from streambanks. Funding provided by the USDA NIFA National Integrated Water Quality Program Project #2013-51130-21484. Quantifying Streambank Resistance to Erosion Fort Cobb Experimental Watershed Unstable streams in the Fort Cobb watershed identified from a 2006 rapid geomorphic assessment (left) and 2008 after tropical storm Erin (right) • Ongoing CEAP research was initiated in 2004 • USDA-ARS has already completed updated calibrated SWAT models of the watershed • Research, Extension, and Outreach Hypothesis: Integrated, watershed-scale biophysical, socioeconomic, and outreach research and activities can effectively identify the most cost- effective and ecologically-beneficial suite of upland, in-stream, streambank and riparian conservation practices (i.e., conversion of highly erodible areas to pasture, implementation of no-till, grade control structures, bank toe protection, bank sloping, cattle exclusion, establishment/protection of the riparian corridor specifically for the Fort Cobb watershed) to reduce sediment loads and protect long-term water availability even under increased climate variability. Nine sites have been selected along two of the major tributaries to Fort Cobb Reservoir: Fivemile (F) and Willow (W) Creeks. At each site a water level logger was installed and cross-sectional surveys performed. Streambanks in the watershed are comprised of a sand or sandy loam while other exhibit a layering effect of sand or sandy loam layers and layers with a higher clay content. Soils samples from the streambeds and each layer of the banks were collected and a particle size distribution analysis performed determine soil texture. Jet erosion tests (JETs) have been used to quantify the erodibility parameters of the streambanks for inputs into the excess shear stress equation: e r = k d (t - t c ) where e r = erosion rate of soil (cm/s); k d = erodibility coefficient (cm 3 /Ns); t = applied shear stress (Pa); and t c = critical shear stress (Pa). Multiple JET test were conducted at each site and each layer. Averages for t c , and k d , for each location are shown below. A higher critical shear stress and lower erodibility coefficient were seen on layers with higher clay content (F2L2, W3L3, and W4L2). This data was also used to explore variability of erodibility parameters on the watershed scale. For the sand layer t c varied by less than one order of magnitude for both creeks and less than two orders of magnitude for the clay layer. At least one cross-section was selected at each site. A portion of Fivemile Creek (Site F2) is heavily impacted by several headcuts. Multiple cross- sections were established at this sites to monitor headcut progression. A longitudinal profile was conducted in July 2014 and again in June 2015. Headcut at Site F2 on Fivemile Creek Progress to Date • Surveys of recreators at Fort Cobb Lake estimated the value of a trip to Ft. Cobb at $56/trip. • A landowner survey (October 2015) in Ft. Cobb showed soil and water conservation enrollment increased with total farm revenue, farmer’s formal education (7 and 38 times more likely for undergrad and graduate respectively), number of years farming, and when the respondent was female (176 times more likely than men). Those who noticed changes in creeks were less likely to have ever enrolled and those with a mindset of downstream stewardship were more 42 times likely to enroll. Rankings of motivations for enrollment are similar between farmers and absentee landowners, but operators valued government programs higher than landlords. • Further developing and evaluating technologies to quantify erodibility properties of streambanks: this work is one of the first uses of a mini jet erosion test (JET) for characterizing erodibility at the watershed scale (Daly et al., 2015, Hydrological Processes, in press). • Knowledge gained includes the variability in erodibility characteristics at the watershed scale for a highly erosive watershed which will provide guidance on how to most appropriately model stream systems. • New non-linear mechanistic detachment models have also been incorporated into process-based models of cohesive streambank erosion (Khanal et al., 2015, Journal of Hydraulic Engineering, in review). • Extension education workshop at the Oklahoma Irrigation Conference in Fort Cobb (August 2014) and also an RVR Meander Workshop for researchers and practitioners (April 2015) Example of aerial bank retreat rates Selected Research Sites in the Fort Cobb Watershed Cross-Section and Profile Surveys Ft. Cobb Agricultural Producers’ Survey Purpose: Learn more about the knowledge, preferences and practices of agricultural producers and landowners in regard to soil conservation in the Ft. Cobb Watershed Variable With Attitudes Without Attitudes PEROWN PEROPRO PERINC 2 PERINC 3 PERINC 4 TFR 2 86.884*** 12.756* TFR 3 25.136* TFR 4 YF 1.096*** 1.072** NS NOTICECH 0.001*** 0.002*** CREEKS 4.683* ST 2 42.597* ST 3 GEN 176.44** 95.636** ED 2 7.032* 5.904* ED3 38.097** 14.524** *, **, *** represent the 90%, 95%, and 99% confidence levels respectively. Odds Ratio Estimates only reported for the Variables that are significant at the 10% level or higher Odds Ratio Estimates of Program Enrollment (CRP, EQIP, CSP, 319, n=67) 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 BenefitsFarm Ecosystem Increases Profit Government Subsity Neighbor showed it works Practice Benefits Downstream Farmer Absentee Landowner Farmer and Absentee Landlord Preference Rankings for Reasons to Adopt Soil and Water Conservation (n=67 , n=36). Streambank Erosion Modeling Process-based models are being used to predict fluvial erosion and geotechnical failure at the site-scale (BSTEM) and reach-scale (CONCEPTS). BSTEM and CONCEPTS inputs included the soil strength parameters (c′ and ϕ′), t c , and k d , channel geometry, and soil layering. Using the cross section surveying results and a SWAT generated hydrograph, for a 2003-2013 study period, BSTEM was ran for six of the watershed sites. Using the same inputs as BSTEM along with bed sediment and soil particle size distributions, CONCEPTS simulations were ran for Fivemile and Willow Creeks for 2008-2013. Long term erosion rates were determined using aerial imagery from NAIP from 2003-2013 and used to calibrate BSTEM and CONCEPTS. F2 F3 F5 W1 W2 W3 Aerial Imagery Retreat (m) 5.0 12.0 11.3 0.0 0.0 7.0 BSTEM Predicted Retreat (m) 6.7 15.6 11.6 2.0 0.0 6.4 BSTEM calibration results 421 422 423 424 425 426 427 428 429 1050 1060 1070 1080 1090 1100 ELEVATION, IN METERS STATION, IN METERS Example BSTEM Retreat (F2) CONCEPTS Thalweg profile change for Fivemile Creek CONCEPTS cross-section change (F5) Photo and cross-sectional survey at F2 below headcuts Thalweg profile change at F2 Sand Clay Loam
