Runoff Estimation, and Surface Erosion and Control Ali Fares, PhD NREM 662, Watershed Hydrology

THE SOIL WATER EROSION PROCESS

EFFECTS ON ENVIRONMENTAL QUALITY AND PRODUCTIVITY LOSS OF OM, CLAY, AND NUTRIENTS REDUCES PRODUCTIVITY LOSS OF OM, CLAY, AND NUTRIENTS REDUCES PRODUCTIVITY DAMAGE TO PLANTS DAMAGE TO PLANTS FORMATION OF RILLS AND GULLIES AFFECTS MANAGEMENT FORMATION OF RILLS AND GULLIES AFFECTS MANAGEMENT SEDIMENTATION IN WATERWAYS, DIVERSIONS, TERRACES, DITCHES SEDIMENTATION IN WATERWAYS, DIVERSIONS, TERRACES, DITCHES DELIVERY OF NUTRIENTS TO SURFACE WATER DELIVERY OF NUTRIENTS TO SURFACE WATER

Quantifying Soil Erosion

Standard USLE plot: 22.1m (72.6 ft) long 22.1m (72.6 ft) long 9% slope 9% slope 4m (13.12 ft) wide. 4m (13.12 ft) wide.

USLE Universal Soil Loss Equation  Wischmeier, W.H. and D.D. Smith Predicting rainfall erosion losses. USDA Agriculture Handbook 537, U.S. Department of Agriculture.

Empirical model: Empirical model: Analysis of observations Analysis of observations Seeks to characterize response from these data. Seeks to characterize response from these data. Based on: Based on: Rainfall pattern, soil type, topography, crop system and management practices. Rainfall pattern, soil type, topography, crop system and management practices. Predicts: Predicts: Long term average annual rate of erosion Long term average annual rate of erosion Subroutine in models such as: Subroutine in models such as: SWRRB (Williams, 1975), EPIC (Williams et al., 1980), ANSWERS (Beasly et al., 1980), AGNPS (Young et al., 1989) SWRRB (Williams, 1975), EPIC (Williams et al., 1980), ANSWERS (Beasly et al., 1980), AGNPS (Young et al., 1989)

The equation: A = R x K x LS x C x P A = average annual soil loss (tons/acre year) A = average annual soil loss (tons/acre year) R = rainfall and runoff erosivity index R = rainfall and runoff erosivity index K = soil erodibility factor K = soil erodibility factor L = slope length factor L = slope length factor S = slope steepness factor S = slope steepness factor C= crop/management factor C= crop/management factor P = conservation or support practice factor P = conservation or support practice factor

R (rainfall and runoff erosivity index) Erosion index (EI) for a given storm: Erosion index (EI) for a given storm: Product of the kinetic energy of the falling raindrops and its maximum 30 minute intensity. Product of the kinetic energy of the falling raindrops and its maximum 30 minute intensity. R factor =  EI over a year / 100 R factor =  EI over a year / 100 A = R x K x LS x C x P

Average annual values of the rainfall erosion index (R).

K (soil erodibility) Susceptibility of a given soil to erosion by rainfall and runoff. Susceptibility of a given soil to erosion by rainfall and runoff. Depend on: Depend on: Texture, structure, organic matter content, and permeability. Texture, structure, organic matter content, and permeability. A =R x K x LS x C x P

Soil-erodibility nomograph.

LS (slope length-gradient) Ratio of soil loss under given conditions to that at a site with the "standard" slope and slope length. Ratio of soil loss under given conditions to that at a site with the "standard" slope and slope length. A =R x K x LS x C x P

Topographic LS factor

C (crop/management) Ratio of soil loss from land use under specified conditions to that from continuously fallow and tilled land. Ratio of soil loss from land use under specified conditions to that from continuously fallow and tilled land. A =R x K x LS x C x P CropFactor Grain Corn0.40 Silage Corn, Beans & Canola0.50 Cereals (Spring & Winter)0.35 Seasonal Horticultural Crops0.50 Fruit Trees0.10 Hay and Pasture0.02 TillageFactor Fall Plow1.00 Spring Plow0.90 Mulch Tillage0.60 Ridge Tillage0.35 Zone Tillage0.25 No-Till0.25

P (conservation practices) Ratio of soil loss by a support practice to that of straight-row farming up and down the slope. Ratio of soil loss by a support practice to that of straight-row farming up and down the slope. A =R x K x LS x C x P Support PracticeP Factor Up & Down Slope1.00 Cross Slope0.75 Contour farming0.50 Strip cropping, cross slope0.37 Strip cropping, contour0.25

USDA Agriculture Handbook 703 (Renard et. al. 1997) USDA Agriculture Handbook 703 (Renard et. al. 1997) USLE factor values: updated, expanded, improved. USLE factor values: updated, expanded, improved. Expanded isoerodents Expanded isoerodents Ponded water on the soil Ponded water on the soil Freeze-thaw cycle and soil moisture Freeze-thaw cycle and soil moisture Complex slopes Complex slopes Conservation tillage and crop rotation Conservation tillage and crop rotation Software Software RUSLE: Revised Universal Soil Loss Equation

WHAT IS RUSLE 2 “GREAT GRANDSON” OF USLE “GREAT GRANDSON” OF USLE MODEL TO PREDICT SOIL LOSS MODEL TO PREDICT SOIL LOSS WHERE OVERLAND FLOW OCCURS WHERE OVERLAND FLOW OCCURS COMPUTES ANNUAL SHEET/RILL EROSION COMPUTES ANNUAL SHEET/RILL EROSION COMPUTES PARTICLE DISTRIBUTION AND RUNOFF COMPUTES PARTICLE DISTRIBUTION AND RUNOFF CROPLAND, FOREST, LANDFILLS, CONSTRUCTION SITES, SURFACE MINES CROPLAND, FOREST, LANDFILLS, CONSTRUCTION SITES, SURFACE MINES WINDOWS “PULL DOWN” MENUS WINDOWS “PULL DOWN” MENUS

WHO AND WHAT OF RUSLE 2 USDA-ARS, USDA-NRCS, VARIOUS UNIVERSITIES USDA-ARS, USDA-NRCS, VARIOUS UNIVERSITIES ON-GOING PROCESS OVER 70 YEARS ON-GOING PROCESS OVER 70 YEARS THOUSANDS OF RESEARCH DATA THOUSANDS OF RESEARCH DATA SET UP WITH VARYING LEVELS OF COMPLEXITY SET UP WITH VARYING LEVELS OF COMPLEXITY COMPUTER REQUIREMENTS COMPUTER REQUIREMENTS WINDOWS 98 WINDOWS 98 INTERNET EXPLORER BROWSER INTERNET EXPLORER BROWSER 64 MB RAM 64 MB RAM DOWNLOAD DOWNLOAD

APPLICABILITY OF RUSLE 2 ESTIMATES INTER-RILL AND RILL EROSION ESTIMATES INTER-RILL AND RILL EROSION ESTIMATES SEDIMENT YIELD FROM OVERLAND FLOW AND TERRACE CHANNELS ESTIMATES SEDIMENT YIELD FROM OVERLAND FLOW AND TERRACE CHANNELS DOES NOT ESTIMATE EPHEMERAL OR PERMANENT GULLIES, MASS WASTING, OR STREAM CHANNEL EROSION DOES NOT ESTIMATE EPHEMERAL OR PERMANENT GULLIES, MASS WASTING, OR STREAM CHANNEL EROSION BEST SUITED TO CROPLAND, BUT IS USEFUL FOR CONSTRUCTION SITES, LANDFILLS, RECLAMATION PROJECTS, AND DISTURBED FOREST LAND BEST SUITED TO CROPLAND, BUT IS USEFUL FOR CONSTRUCTION SITES, LANDFILLS, RECLAMATION PROJECTS, AND DISTURBED FOREST LAND

APPLICABILITY OF RUSLE 2 (cont.) BEST WHERE RAINFALL IS REGULAR AND EXCEEDS 20”/YR. BEST WHERE RAINFALL IS REGULAR AND EXCEEDS 20”/YR. MEDIUM-FINE TEXTURED SOILS MEDIUM-FINE TEXTURED SOILS SLOPES 3-20% AND LESS THAN 600 FT. SLOPES 3-20% AND LESS THAN 600 FT. BEST AT CALCULATING “AVERAGE ANNUAL SOIL LOSS”, NOT RECOMMENDED FOR SINGLE STORM EVENTS BEST AT CALCULATING “AVERAGE ANNUAL SOIL LOSS”, NOT RECOMMENDED FOR SINGLE STORM EVENTS

RUSLE 2 FACTORS A = R x K x LS x C x P CLIMATE (R) AND SOIL (K) FACTORS ARE SET FOR A GIVEN FIELD CLIMATE (R) AND SOIL (K) FACTORS ARE SET FOR A GIVEN FIELD SLOPE GRADE (S) AND LENGTH (L) CAN BE ADJUSTED WITH DIFFICULTY SLOPE GRADE (S) AND LENGTH (L) CAN BE ADJUSTED WITH DIFFICULTY MOST FLEXIBILITY WITH COVER MGT. (C) AND SUPPORTING PRACTICES (P) MOST FLEXIBILITY WITH COVER MGT. (C) AND SUPPORTING PRACTICES (P)

EROSION CONTROL PRACTICES Structures: diversions, terraces, waterways Reduce slope length Reduce slope length Slow runoff velocity Slow runoff velocity Divert excess water safely Divert excess water safely Avoid runoff over barnyard, feedlots, etc. Avoid runoff over barnyard, feedlots, etc.

CONTOUR TERRACES Grant Co.

EROSION CONTROL PRACTICES Management practices Cover crops Cover crops Crop residue management Crop residue management 30% residue reduces erosion 50-60% 30% residue reduces erosion 50-60% Contour tillage Contour tillage Slope < 8% and 300’ long Slope < 8% and 300’ long Contour strip cropping and buffers Contour strip cropping and buffers Alternating sod strip for steep land Alternating sod strip for steep land

Controlling Water contaminants at the Source, Kaiaka-Waialua Watershed

Kaiaka and Waialua bays, are water quality limited segments due to high levels of total P, NO - 3, chlorophyll a, and turbidity exceeding the maximum allowable levels (HI-DOH). Kaiaka and Waialua bays, are water quality limited segments due to high levels of total P, NO - 3, chlorophyll a, and turbidity exceeding the maximum allowable levels (HI-DOH). Sediment loads from agricultural lands and effluent discharged from household cesspools are two of the major sources of pollution. Sediment loads from agricultural lands and effluent discharged from household cesspools are two of the major sources of pollution. Sediment losses are generated from cropped and fallow zones as a result of an intensive agricultural system that includes a crop/fallow cropping combination. Sediment losses are generated from cropped and fallow zones as a result of an intensive agricultural system that includes a crop/fallow cropping combination.

Objectives The goal of this project is to implement and demonstrate erosion control practices to help manage erosion throughout Kaiaka- Waialua watershed, thereby reducing sediment and potential pollutant loads (P, N) into the surface water resources, and consequently improving water quality of the coastal area. The goal of this project is to implement and demonstrate erosion control practices to help manage erosion throughout Kaiaka- Waialua watershed, thereby reducing sediment and potential pollutant loads (P, N) into the surface water resources, and consequently improving water quality of the coastal area.

Materials and Methods Field in a commercial farm, Field in a commercial farm, Ewa Silty clay soil, a mean Ksat = 3.5 cm d -1 (Candler 15 m d -1 ) Ewa Silty clay soil, a mean Ksat = 3.5 cm d -1 (Candler 15 m d -1 ) Three cover crops (Sunn hemp, Sudex & Oats) were replicated 3 times in a RCB design. Three cover crops (Sunn hemp, Sudex & Oats) were replicated 3 times in a RCB design. Suction cups were installed in each plot to collect soil solution Suction cups were installed in each plot to collect soil solution Surface runoff was collect from each plot following rainfall. Surface runoff was collect from each plot following rainfall. Soil water contents (10,20,30 & 50cm) from each treatment Soil water contents (10,20,30 & 50cm) from each treatment

Materials and Methods Soil physical properties were determined: Ksat, BD & soil water release curve Soil physical properties were determined: Ksat, BD & soil water release curve Soil samples were collected before, in the middle and at the end of the trial. Soil samples were collected before, in the middle and at the end of the trial. Total dissolved and total suspend solids (TDS, TSS) were determined (EPA’s 160.1, methods) Total dissolved and total suspend solids (TDS, TSS) were determined (EPA’s 160.1, methods) NO3, NH4 and P were determined by UH-ADSC NO3, NH4 and P were determined by UH-ADSC

Materials and Methods

Subsurface Water Quality Analysis Collected soil solution samples were analyzed at the University of Hawai’i (ADSC) for: Collected soil solution samples were analyzed at the University of Hawai’i (ADSC) for: Ammonium Ammonium Nitrate Nitrate Total Nitrogen and Total Nitrogen and Phosphorus Phosphorus

Results Runoff water quality Runoff water quality Subsurface water quality Subsurface water quality

March March 22 March 25 March 31 April 7 April 18 April 22 April 27 May mm occurred in 11 hr, 2/27 at a rate of 24 mm hr-1

March April May Variable TSSNSNS****NS***** TDSNSNSNSNSNSNSNS**NSNS Nitrate*NSNS*NS**NS**NS** AmmoniumNSNSNS****NS**NS**NS TN*NSNS********NS**NS PhosphorousNSNSNSNSNSNSNS****** *, ** denotes a significant or highly significant difference was detected between treatment means, respectively. ANOVA Runoff Results

Sunn hemp Oats Fallow Sudex Surface Runoff Collection

Runoff water Quality TSS, 70% there was statistically significant treatment effect TSS, 70% there was statistically significant treatment effect Nitrate, 50% there was statistically significant treatment effect Nitrate, 50% there was statistically significant treatment effect Ammonium, 40% there was statistically significant treatment effect Ammonium, 40% there was statistically significant treatment effect TN, 60% there was statistically significant treatment effect TN, 60% there was statistically significant treatment effect

Removal Efficiencies Calculation for Removal Efficiencies (RE): Calculation for Removal Efficiencies (RE): RE = [1- (Cover Crop (g) / Fallow (g))]x100 RE = [1- (Cover Crop (g) / Fallow (g))]x100 A positive RE means that there was a reduction in pollutant levels in comparison to the fallow A positive RE means that there was a reduction in pollutant levels in comparison to the fallow A negative RE means that there was an increase in pollutant levels in comparison to the fallow treatment A negative RE means that there was an increase in pollutant levels in comparison to the fallow treatment

Date3/33/163/223/253/314/74/184/224/275/18AVG Rainfall (mm) Sudex Sunn Hemp Oats Oats Removal Efficiencies for TSS

Date3/33/163/223/253/314/74/184/224/275/18AVG Rainfall (mm) Sudex Sunn Hemp Oats Oats Removal Efficiencies for Total Dissolved Solids

A A A A B A B B

Date3/33/163/223/253/314/74/184/224/275/18AVG Rainfall (mm) Sudex Sunn Hemp Oats Oats Removal Efficiencies for Total Nitrogen

B A B AB A A A A

Date3/33/163/223/253/314/74/184/224/275/18AVG Rainfall (mm) Sudex Sunn Hemp Oats Oats Removal Efficiencies for Ammonium

Soil Solution Samples ANOVA Variable3/223/253/314/7 Nitrate*****NS AmmoniumNSNSNSNS TN*****NS PhosphorousNSNSNSNS * denotes a significant difference was detected ** denotes a highly significant difference was detected

AB B B A

B B A

B A B B

Summary & Conclusions The presence of cover crops reduced the nitrate and total nitrogen levels in the soil solution compared to the fallow treatment regardless of the sampling date. The presence of cover crops reduced the nitrate and total nitrogen levels in the soil solution compared to the fallow treatment regardless of the sampling date. 95 to 97% of the total nitrogen collected was nitrate. 95 to 97% of the total nitrogen collected was nitrate. The sunn hemp treatment had the second highest nitrate and total nitrogen levels after the fallow treatment. The sunn hemp treatment had the second highest nitrate and total nitrogen levels after the fallow treatment.

Statistical Analyses Results There were statistically significant effects of the cover crops on: There were statistically significant effects of the cover crops on: Nitrate and total nitrogen for all reported sampling dates: March 21, 25, 31 & April 7 Nitrate and total nitrogen for all reported sampling dates: March 21, 25, 31 & April 7 However, cover crops effect was not statically significant for: However, cover crops effect was not statically significant for: Ammonium and Total Phosphorus Ammonium and Total Phosphorus

CONTOUR STRIP CROPPING Crawford CO

Terracing & Contour Farming

References Millward, A. A., and Mersey, J. E.,(1999) Adapting the RUSLE to model soil erosion potential in a mountainous tropical watershed, Catena, 38(2), DeRoo A.P.J. (1998) Modelling runoff and sediment transport in catchments using GIS. Hydrological Processes 12(6), Millward, A. A., and Mersey, J. E.,(1999) Adapting the RUSLE to model soil erosion potential in a mountainous tropical watershed, Catena, 38(2), DeRoo A.P.J. (1998) Modelling runoff and sediment transport in catchments using GIS. Hydrological Processes 12(6), du/cropsyst/manual/sim ulation/soil/erosion.htm du/cropsyst/manual/sim ulation/soil/erosion.htm du/cropsyst/manual/sim ulation/soil/erosion.htm du/cropsyst/manual/sim ulation/soil/erosion.htm WOLKOWSKI, D.Soil Science Dept. UW-Madison. WOLKOWSKI, D.Soil Science Dept. UW-Madison.