Watershed Assessment

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Watershed Assessment

• Objective determine the impact of project
  interventions on the biophysical condition of the
  watershed (specifically land cover changes,
  water resources, and soil erosion)
• What is the current situation?
• What is the impact of project interventions
• The goal is to help answer the question Is the
  project having a positive impact on natural
  resource management and sustainable agriculture ?

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This presentation

• Background on the project area
• Assessment of the current condition
• Preliminary modeling results showing practice
  impacts

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Luangwa River Valley Physiographic Regions

• Three basic physiographic regions
• Valley floor
• Hills / hilly region
• Plateau / upland area
• Differences in regions
• Soils (fertility, erodibility) and vegetation
• National forest Hills
• National parks - valley

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Luangwa River Valley Physiographic Regions

• Relationship of physiographic regions to
• National parks
• National forests
• COMACO units and depots

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Focus for this study
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Valley Floor
Mopane forest
Groundnuts Maize
Cotton
Rice
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Valley Floor - runoff and erosion

• Mopane is expansive clay soils
• Potentially high runoff after re-wetting
• Cropland
• Generally low slopes
• Some evidence of runoff and rill erosion
• (limited observations)

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Plateau Land Use
Cropland maize, groundnuts, cotton
Dambo grassed wetland drainageway -
wetland filter in rainy season - cattle
grazing in dry season
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Plateau agriculture
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Plateau agriculture
Productivity
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Plateau agriculture
Productivity
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Plateau agriculture
Productivity
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Plateau runoff and erosion
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Plateau runoff and erosion

• Little runoff from fields
• Low slopes
• High infiltration
• High roughness in tillage
• Runoff and erosion from paths and roads

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Hill region
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Hill region - runoff and erosion

• Runoff from fields
• Low to moderate slopes
• Less permeable soils
• Erosion evident in fields
• Erosion in tracks / roads
• Gullies developing

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What is happening in the streams?
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Primary Areas of Interest
Slope
River monitoring
Dambo watersheds
Paired watersheds
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Dambo Watersheds - Emusa
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Paired Forest/Ag. Watersheds
Khuyu school
Chazovu school
Kamwamphula
Luelo
ZAWA gate
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Comparison of Flow and Quality
Dambo
Agricultural
Forested
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Comparison of Flow and Quality
Dambo
Agricultural
Forested
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Comparison of Flow and Quality
Dambo
Agricultural
Forested
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Potential Flow Gauging Locations
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Preliminary monitoring Mar 2007

• Flow gauging
• Flow velocity estimates

Lunzi River
Kamwamphula River
Kanyanga Dambo
River Survey Crew
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Lunzi River near Manga School
15 March 2007
Estimated flow rate 23.24 m3/s
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Continued monitoring - 2007

• Manga staff
• Cross-sections and flow velocity of the three
  rivers monthly (3-4 times until the flow stops)
• Record depth to water in village wells weekly
• Emusa staff
• Monitor 4 upland catchments - weekly measure
  depth of water
• Monthly take cross-section and velocity

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Preliminary Modeling Study
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Study Area

• Three watersheds Focus for this study

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Data

• Zambia Meteorological Service
• Historical weather data of 21 years
• Rainfall and temperature (average, max., and
  min.)
• Annual average rainfall 855mm
• Maximum daily rainfall 96.5mm
• Temperature range 6 39C
• Clear dry and wet season
• Dry season
• May Oct
• Wet season
• Dec Mar

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Data

• Topography
• Resampled DEM from finished SRTM-3 (90m)
• Shuttle Radar Topography Mission for the entire
  earth of 80
• USGS EROS (Earth Resource Observation and
  Science)
• Derived properties from the data
• Average elevation 1,035m
• Average slope 3.73
• Stream Line
• Extracted from Landsat7 ETM
• Virtually from 7-3-2 band combo
• Derived from the DEM (SRTM-3)
• Flow accumulation
• Compared and corrected
• stream burning on the DEM
• with the extracted stream line

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Data

• Soil
• FAO DSMW (Version 3.6, Jan 2003)
• 26 major soil groupings and 106 soil units
• 15M scale, Covers entire countries in the world
• Properties acquired from the Digital Soil Map of
  the World
• Soil texture, drainage level, No. of layers, so
  on
• Soil properties of the study area
• Dominant texture
• Sandy-clay-loam loam
• Regional distribution
• Plateau Well drained (Ferrsols)
• Hill Moderated drained (Lithosols)
• Valley Poorly drained (Luvisols)

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Data

• Land use
• Land use classification
• Landsat7 ETM (30m, May 8 2002)
• Object data, May 8 2002
• Quickbird (2.4m, July 23 2002)
• Reference groundtruth

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Modeling Scenarios

• Current land use
• Scenario1 original all forest (no cropland)
  
• Scenario2 Expanded cropland in forest area
• Assume hill region with slopes lt 4 are cleared
  for crops

Current (2002)
Current (hill region)
Future (Scenario 2)
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Scenario Expanding Cropland in Hill Region
Impact on mean runoff from a 70mm storm
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Results

• Seasonal variation of flow (Lundazi)

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Results

• Flooding probability for 3 scenarios

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Results

• Sediment yield probability for 3 scenarios

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Preliminary conclusions

• Crop production is best in the plateau areas
• Good soils, low slopes, low runoff
• Dambos provide natural filtering and flow
  attenuation function
• Dambos and their function in the landscape should
  be preserved
• Hill region has higher runoff and erosion due to
  steeper slopes and shallow less-permeable soils
• Improving sustainability and productivity of
  upland cultivation benefits all valley ecosystems

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Expansion of cropland
exhausted fertility
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Continuing activities

• Quantifying hydrologic response at various scales
  and for different landscape systems
• Documenting change in land use
• May/June 2007 satellite imagery and aerial
  photography
• Incorporate data and results of soils and
  productivity research into watershed modeling

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Acknowledgements

• Cornell University
• Alfonso Torres
• Noha Abou-Madi
• Beth Buckles
• Duane Chapman
• Jon Conrad
• Parfait Eloundou-Enyegue
• John Fay
• Peter Hobbs
• George Kollias
• Johannes Lehmann
• Benjamin Lucio
• Carmen Moraru
• Alice Pell

• Wildlife Conservation Society
• Dale Lewis
• Steve Osofsky
• David Moyer
• Virginia Tech University
• Conrad Heatwole
• Keith Moore
• Theo Dillaha
• Tropical Soil Biology Fertility
• Robert Delve

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Questions?