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

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