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Management for Water Yield

Management for Water Yield. Basic treatments Removal of woody vegetation Weather modification Construction of “catchments”. Mgt. Treatments Vary by Zone. Alpine zone Region above tree line Snowpack zone Area immediately below alpine zone. Mgt. Treatments Vary by Zone.

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Management for Water Yield

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  1. Management for Water Yield • Basic treatments • Removal of woody vegetation • Weather modification • Construction of “catchments”

  2. Mgt. Treatments Vary by Zone • Alpine zone • Region above tree line • Snowpack zone • Area immediately below alpine zone

  3. Mgt. Treatments Vary by Zone • Forests outside snowpack zone • Woodland and brushy zone • Chaparral, • Oak savanna, • Pinon-Juniper woodland

  4. Mgt. Treatments Vary by Zone • Phreatophyte zone • Plants that obtain moisture primarily from ground water or capillary fringe just above ground water. • Occur along stream bank and in flood plain

  5. Mgt. Treatments Vary by Zone • Low shrub and grassland zone

  6. Alpine Zone • Characteristics of zone • Snow persists well into summer • Summer snow fields almost immune to net evaporation • Major contributor to summer runoff • Mgt. Options • Snow fences and tree planting used to strategically place snow banks relative to sun

  7. Snowpack Zone • Covers largest land area • Mostly coniferous and in western U.S., but some in East • Mgt. Options • Clear-cut – In Arizona this increased stream flow from equivalent of 0.6 to 13.5 inches of precipitation

  8. Forests Outside Snowpack Zone • Many vegetative manipulation options • Reduce woody cover • Coweeta, NC • Increase after clearcutting was 11 to 16 inches on north slopes, much less on south slopes • Cascade Mt., OR • Increase after was clearcutting 18 to 21 inches

  9. Woodland and Brushy Zone • Vegetative manipulation less effective • Removal increased yield from 0 to 7 inches depending on rainfall and cover type Oak Savanna

  10. Phreatophyte • Very high evapo-transpiration losses • Manipulation studies inconclusive • Catchment areas main tool

  11. Low Shrub and Grassland Zone • Drier sites • Few if any management options • Use catchments to retain runoff

  12. Control of Yield Must Consider Timing and Amount of Flow Gaging Station

  13. Control of Stream Flow Regimen • Objectives • Prevent deterioration of regimen because of altered land uses • Improve natural stream flow regime by management of hydrology • Rehabilitate deteriorated watersheds Stable banks, woody vegetation

  14. Primary considerations • Irregular flow • Volume of high and low flows • Duration of high and low flows • Capacity of structures to handle high flows • Management of aquatic ecosystems Hyetograph

  15. Influencing Factors and Controls • Flow of water from disturbed areas • Route runoff into percolation area, not directly into channel • Reduce runoff by maintaining permeability • Timing of runoff • Limited possibilities • Some control of snow storage and melt

  16. Influencing Factors and Controls • Modify timing and amount of evaporation • Synchronize inflows to channels by modifying watershed characteristics, e.g. catchments

  17. Management in Alpine Zone • Modify snow melt – concentrate drifts at higher elevations • Control route of melt water to maximize infiltration, use earthworks to catch runoff from damaged areas

  18. Management in Forest Snow Pack Zone • Modify snow melt by managing forest cover, e.g. smaller openings reduce melt rate • Route runoff to infiltration areas • Modify synchronization of inflows to channels by varying cover among units

  19. Forests Outside Snow Pack Zone • Winter operations possible but soil damage likely • Abused soil leads to rapid runoff, erosion and low summer flows • Restoration of forest cover is usual treatment

  20. Woodland and Brushy Zone • Limited options • Control wildfires that expose soil

  21. Phreatophyte Zone • Removal of vegetation may reduce diurnal variation

  22. Low Shrub and Grassland Zone • Maintaining or restoring native vegetation critical

  23. Control of Water Quality • Surface erosion control • Timber harvesting • Grazing • Mining Acid Mine Drainage, Clearfield, PA

  24. Surface Erosion Control • Avoid critical point in erosion –revegetation cycle • Revegetate exposed soil as soon as possible

  25. Surface Erosion Control • Control mass movement

  26. Surface Erosion Control • Prevent channel cutting by controlling streamflow energy

  27. Timber Harvesting • Major factor in control of water quality • Felling, limbing and bucking – avoid riparian zones and exclude slash from channel

  28. Timber Harvesting • Skidding and yarding – minimize soil compaction and disturbance • Use high lead systems in sensitive and steep areas

  29. Timber Harvesting • Roads and skid trails – layout and construct according to BMP’s

  30. Grazing • Grazed land usually easily damaged • Removes organic matter • Compacts soil • Balance forage growth and consumption

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