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Potential
for Payment for Environmental Services (PES) approaches to contribute
to equitable and sustainable management of soil and water in upper
catchments
Soil and Water Assessment Tool (SWAT) training workshop
by Francis Gichuki (Training Facilitator)
and
Fredah Maina (Workshop Coordinator)
Introduction
Scientists now face new challenges arising from the complexity of having to address issues in a holistic manner. To respond effectively to these challenges scientists have to greatly expand their repertoire of skills and knowledge. The Challenge Program on Water and Food (CPWF) through the activities of Theme 2 (Water and People in Catchments) and Theme 4 (Integrated Basin Water Management System ) contributed to this capacity building challenge by organizing a five day training workshop for soil scientists on SWAT held between 6th - 10th August, at the ICRAF Campus in Nairobi, Kenya. The workshop was supported financially by Payment for Environmental Services (PES) project of Theme 2.
The training workshop was to improve the participating researcher’s skills to use of the Soil and Water Assessment Tool (SWAT) in hydrological modeling to determine the impact of soil technologies on the landscape/watershed. Its specific objective was to improve the capacity of the AfNet members in conducting soil research that results in, not only plot level sustainability, but also ensure landscape scale watershed management/stability in the Africa.
The workshop was attended by 12 participants, 8 from Kenya, 2 from Tanzania and 2 from Uganda. 6 of these participants (2 from each country) were from the NARS.
Workshop contents
Nyando Basin in Kenya was used as the study area and the training was geared to answering the question: can better soil management at field/farm level contribute to enhancing basin-wide benefits sustainably and equitably. The workshop sessions include:
- Introduction to Nyando Basin natural resources and socio-economic issues
- SWAT model overview and ARCVIEW and AVSWAT commands and operations
- Basin delineations and characterization (processing topographic, soil and land use data)
- Land management (plant characteristics and management data)
- Water management (ponds and reservoir data)
- Interpretation of results
- Setting management scenario (land use change, changes in cropping system management - conservation tillage and use of manure and fertilizer)
- Improving model accuracy (data quality, calibration and validation).
Most of the time was spend in acquiring hands on experience in running the model and formulating modeling scenarios. Real field experiences in the Nyando Basin presented by the participants and by Dr. Alex Awiti reinforced the workshop material and training. Mr. Job Kihara illustrated how DSSAT model could complement SWAT model by generating some of the crop growth modeling data required by SWAT.
About Soil and Water Assessment Tool (SWAT) |
The Soil and Water Assessment Tool (SWAT) is a physically-based hydrologic model that is used to predict the impact of changes in (a) land use and management practices and (b) water development and use on surface and groundwater, erosion and sedimentation, water quality, plant biomass and yield. The model can simulate changes in complex basins with varying soils, land use, and management conditions over long periods of time. The model subdivides a basin into sub-basins and for each sub-basin the area is further subdivided into homogenous hydrologic response units (HRUs) having unique soil and land use properties. The loading and movement of runoff, sediment, nutrient and pesticide loadings is simulated in each sub-basin and routed through the main channels.
The input data include topography, soil, land use, weather, characteristics of main channels and groundwater aquifer, plant growth characteristics, land management (tillage, planting, fertilizer application, irrigation, weeding, grazing and harvesting) and water management (water use, water pollution discharges and location, characteristics and operation regime of ponds and reservoirs).
The main outputs of SWAT model are:
- Water, nutrient, sediment and pesticide balances for each HRU, sub-basin, and river reach.
- Soil nutrient, organic matter and water balances for each HRU
- Plant growth, evapo-transpiration, water, temperature, nitrogen and phosphorus stress, biomass and yield
SWAT model and its manuals can be downloaded from the web site (http://www.brc.tamus.edu/swat/avswat.html). |
Comments by workshop participants and follow up activities
The participants were pleased to note that the model though requiring a lot of data was relative easy to run. Within two days they were able to carry out simulations with default data sets.
They also noted that most of the data might not be readily available, especially in Uganda and Tanzania. They specifically identified the need to work closely with land resources and soil survey units to ensure that the required data is available at the appropriate spatial and temporal resolution.
The participants identified follow up SWAT simulation studies that they will undertake shortly.
These input received from the workshop will contribute towards the follow up workshop that will be held later in October on a tool focusing on the economic, social and environmental evaluation of land-uses (ECOSAUT). The output from SWAT will feed into the background for the ECOSAUT analysis to give biophysical (SWAT), socio-economic and environmental outputs for environmental sustainability in the watershed.
Seated from right to left: A. Bationo (AfNet Coordinator), J. Odongo, F. Gichuki (Course facilitator) and B. Waswa
Standing (right to left): J. Mukalama, J Kihara, K Kaizzi, O Semalulu, J Meliyo,
N Sanginga (Director, TSBF), Z Mkangwa, A Esilaba, P Kamoni and F Maina
Not in photo: J Okeyo and T Yatich
AfNet – African Network for soil biology and fertility (Network within TSBF-CIAT and FARA)
For more information contact: Francis Gichuki (Training Facilitator) (f.gichuki@cgiar.org) and Fredah Maina (Workshop Coordinator) (f.maina@cgiar.org)
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