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 • Forests outside snowpack zone • Woodland and brushy zone • Chaparral, • Oak savanna, • Pinon-Juniper woodland

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Phreatophyte Zone • Removal of vegetation may reduce diurnal variation

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

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

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

Surface Erosion Control • Control mass movement

Surface Erosion Control • Prevent channel cutting by controlling streamflow energy

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

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

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

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

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