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

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


• 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


• 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


• Control mass movement


• 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

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

Documents

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