1. RANGELAND HYDROLOGY BASIC CONCEPTS Lamar Smith Cascabel Ranch and Consulting Carta Valley, Texas

2. OBJECTIVES  Understand water balance  Understand basic erosion processes on rangeland  Understand how brush control affects water yield and erosion

3. Precipitation Runoff Infiltration Evaporation Transpiration Transmission losses Groundwater recharge Summarizing Hydrologic Data Water balance – an accounting method

4. Annual Water balance for the Upper San Pedro River

5. Annual Water Balance for the Walnut Gulch Experimental Watershed Ephemeral tributary to San Pedro River RAINFALL 12 in. ( 305 mm ) SURFACE DETENTION & INFILTRATION 10 in. ( 254 mm ) EVAPORATION & TRANSPIRATION 10 in. ( 254 mm ) ONSITE RUNOFF 2 in. ( 51 mm ) CHANNEL LOSSES 1 3/4 in. ( 45 mm ) SURFACE RUNOFF 1/4 in. ( 6 mm ) EVAPORATION & TRANSPIRATION FROM CHANNEL AND VEGETATION ALONG STREAM GROUND WATER RECHARGE FROM CHANNEL WATERSHED

6. EROSION PROCESSES RHEM MODEL Climatic data  Climatic data  Soil texture  Slope length  Slope shape  Slope %  % bunchgrass, forb/annual, shrubs, sod grass canopy cover  % rock, basal plant, litter and cryptogam cover Most of these factors are climatic and site related – only vegetation is manageable

7. STREAM FLOW (WATER YIELD)  Subsurface = Springs  Runoff = Flooding – dirt tanks, etc.

8. FFOLLIOTT AND THORUD – 1975  Increase in Water YieldPrecipitation  Mixed conifer = 6 inches 24+ inches  Ponderosa Pine = 2 inches20-24 inches  Chaparral = 4 inches 16-20 inches  Pinyon – Juniper = 0 inches16-20 inches  Grassland = 0 inches 12-16 inches  Desert Shrub = 0 inches8-12 inches

10. MAIN POINTS  Infiltration – greater on sandy soils  Depth of penetration – greater on sandy soils - gravel increases  Evaporation – less on sandy soils  Deep percolation – greater on coarse soils – winter precip  Season of precipitation vs plant growth

11. DOES BRUSH CONTROL REDUCE SEDIMENT/EROSION?

12. MOST STUDIES SHOW THAT MESQUITE CONTROL REDUCES RUNOFF AND SOIL EROSION.  Mesquite reduces grass cover  Increases patchiness of ground cover

13. STUDIES IN CREOSOTEBUSH ARE LESS DEFINITIVE  How treated? Roughness factor.  How much grass response?  Soil depth, texture?  Storm intensity?

14. SO WHY DO BRUSH CONTROL?  Reduce erosion  Reduce runoff intensity - flooding  Increase species diversity  Increase life form diversity  Increase food for wildlife and livestock  Improve biological production????