Watershed Conservation Management Planning Using the Integrated Field & Channel Technology of AnnAGNPS & CONCEPTS Eddy Langendoen Ron Bingner USDA-ARS National Sedimentation Laboratory, Oxford, Mississippi
BMP s can be studied from field scale to their impact on a watershed scale. Field scale BMP A watershed with diverse landuse, including BMPs.
Erosion can occur anywhere in a watershed Erosion in fields Erosion in small field channels Erosion in stream systems
Tillage-Induced Ephemeral Gully Erosion - TIEGEM As a result of a non-erosive layer at the bottom of the tillage depth
Branching of Ephemeral Gullies
Disturbed Stream Systems
AnnAGNPS A partnering effort between the USDA: Agricultural Research Service and Natural Resource Conservation Service National Sedimentation Laboratory
CONCEPTS CONservational Channel Evolution and Pollutant Transport System CONCEPTS simulates long-term response of channels to loadings of water and sediments, and to instream structures Bendway weir Streambank erosion Bed evolution and sediment transport Flow hydraulics Input: Output: Channel geometry Composition of bed and bank materials Erosion resistance and shear strength of bed and bank materials Rates of flow and sediments entering the channel Changes in channel geometry Time series of hydraulic variables and sediment yield
TYPES OF EROSION Interrill and rill (sheet-rill) Wind Ephemeral gully Permanent, incised (classical) gully Stream channel Mass movement Geologic
Watershed Erosion Model Components Sheet & Rill Ephemeral Gully Classical Gully Channel Erosion RUSLE EGEM REGEM TIEGEM Runoff/Sediment Relat. CONCEPTS when significant changes of channel morphology are possible
Watershed Sedimentation Processes ARS Models CONCEPTS RUSLE Surface Erosion AnnAGNPS Hillslope Gully Erosion Hillslope Storage REMM Mass Erosion Channel Transport Net Watershed Sediment Yield Channel Bank Erosion Channel Storage Yield Storage and Transport Production
RUSLE EROSION Concentrated Flow Sediment and nutrients transported to the edge of the field.
AnnAGNPS Cell Landscape Overland flow Interrill Rill Ephemeral Gully (Concentrated flow) Erosion Types
Water, Sediment, & Chemical Sources Track loadings by source throughout the transport process Cell A reach 1 gully Cell B reach 2 reach 3 Cell C feedlot Cell D Impoundment point source Cell E reach 4 watershed outlet Cell F
AGNPS WATERSHED DESCRIPTION FOCUS ON STREAM REACHES by CONCEPTS SUBWATERSHEDS CONNECTED BY THE CHANNEL NETWORK
Reach Processes AnnAGNPS Incorporates simple reach routing processes. There is no memory between runoff events.
Reach Processes CONCEPTS is better suited: When a significant portion of sediment originates from channel sources. When hydrodynamic channel morphological process simulations are needed.
Integration of REMM Within Models Riparian Buffer System Stream Field Erosion and Deposition
Case Study James Creek, MS Listed as impaired due to excessive sedimentation Channel impacted by: Channelization (~1905) Dredging and snagging (1968) Construction of several lowwater crossings (1960s 1990s) Construction of Tennessee- Tombigbee waterway (1980s).-, 55 Monroe #S Aberdeen #S Jackson.-, 20.-, 59 Flow direction
James Creek Description 1430 mm rainfall Drainage area 111 sq km (43 sq mi) Soils: dominated by silty clays and silt loams Most of the watershed in cultivated croplands, pasture or fallow conditions Main crops: corn, soybeans, cotton, wheat, and sorghum Implemented BMPs: reduced tillage, strip cropping, terraces
James Creek Channel Characteristics Lower 6.6 km has natural sinuous alignment Bank erosion is prevalent Boundary materials are predominantly silts and clays
DETERMINATION OF ACTUAL SEDIMENT LOADINGS AT THE OUTLET OF JAMES CREEK DARRACOTT ROAD OUTLET JAMES CREEK OUTLET CONCEPTS MAIN CHANNEL ANNAGNPS TRIBUTARIES SEDIMENT FROM MEASURED CROSS SECTIONS SEDIMENT FROM ANNAGNPS
GIS Landuse Layer PLANTING SOYBEANS INTO HARVESTED WHEAT FIELDS GULLY MIGRATION INTO FURROWS LANDUSE TYPE CORN SOYBEANS IN A REDUCED TILLAGE FIELD COTTON FALLOW FOREST PASTURE SORGHUM SOYBEANS URBAN WHEAT
Synthesis of 1967 Cross-Sections THALWEG ELEVATION, IN METERS 80 75 70 65 60 55 50 45 1967 2002 Floodplain Low-water crossing Sinuous reach Channelized reach 0 5 10 15 20 25 DISTANCE ABOVE MOUTH OF JAMES CREEK, IN KILOMETERS
YEARLY RAINFALL FROM ABERDEEN, MISSISSIPPI 1967-2001 PRECIPITATION (mm) 2000 1600 1200 800 1970 1980 1990 2000 YEAR 1967-2001 AVERAGE (1411 mm) LONG-TERM AVERAGE (1317 mm)
ANNAGNPS SIMULATED YEARLY RUNOFF AT DARRACOTT ROAD RAINFALL or RUNOFF (mm) 2000 1600 1200 800 400 RAINFALL RUNOFF 0 1960 1970 1980 1990 2000 YEAR
AnnAGNPS Simulated Runoff and Sediment Yield by Field 31-100 100-169 169-238 238-307 307-376 376-446 446-515 515-584 584-653 653-722 mm/y 0-4.1 4.1-8.3 8.3-12.4 12.4-16.5 16.5-20.6 20.6-24.8 24.8-28.9 28.9-33 33-37.1 37.1-41.3 T/ha/y 484 mm/y Sediment Load Portion from Upland Sources @ Outlet = 2.2 T/ha/y (1 t/ac/y)
Comparison of Cross Sections 66 70 ELEVATION, IN METERS 65 64 63 62 61 60 1967 Initial Condition 2002 Measured 2002 Simulated 59-20 0 20 40 60 80 69 68 67 66 65 64 432+10 63 548+70 62 0 20 40 60 80 100 120 HORIZONTAL DISTANCE, IN METERS
Sediment Load 10000000 SEDIMENT LOAD, IN TONNES 1000000 100000 10000 1000 All channels Fields Total 100 1965 1970 1975 1980 1985 1990 1995 2000 YEAR
Sediment Load at the Watershed Outlet (1967 2002) Total Sediment Load Reach Channel Sheet and Rill Total (T) (T) (T) Above rkm 7.92 7220000 910000 8130000 Below rkm 7.92 677000 53340 730000 Total Load (T) 7900000 964000 8860000 Average Load (T/y) 226000 27500 253000 Average Yield (T/y/km 2 ) 2015 246 2260 Contribution (%) 89 11 -
Summary AnnAGNPS is a watershed conservation planning tool (CEAP). CONCEPTS provides needed capabilities to characterize channel erosion contributions. Used together these technologies allow watershed management planning to target the appropriate issues.
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