Webpages with more detailed information.
Discussion Development
Environmental Impacts
Management inputs
Information System
A GIS/Remote Sensing system has been introduced for the purpose of project management (by monitoring) and O&M planning. This Information System can be considered a Management Information System (MIS). It worked well to locate places where the O&M did not proceed according planning.
Three types of data were used:
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Field survey data obtained during the early implementation phase of the project, |
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Systematic acquired new data of key indicators for monitoring purposes, and |
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Remote Sensing data obtained during the most recent wet season, based on Radarsat Images (10 m resolution). |
Topographical maps with local coordinates at scale 1:5,000 were used to create DEM’s (Digital Elevation Models). Spot heights were digitized on screen. For digitizing of land use, the canal lay-out and the infrastructure of the schemes, the geo-coded Radarsat images were used, beside existing topographical maps and other field information. Ground control points appear to have a RMS (Root-Mean-Square) error of about 20-m.
DEM of Dendang based on field data. Lay-out, Geo-coded map and Land use during planting
Modeling of DEM’s created new thematic maps. Based on the DEM’s and by overlay of a number of soil/hydrological and land use maps these modeled thematic maps were created. The result is a combination of the hydro-topographical characteristics of the land corrected for the expected subsidence and specific soil conditions having an influence on potentials. The resulting mapping units are used for O&M and design recommendations. They are expressed in Water Management Zones, which are land units based on relevant physical characteristics of the land and the dominant land use (or agreed future land use). A basic idea of the system is that Farmer Groups and other users will be able to compare the actual situation with future potentials and infrastructure options.
It is very important in Tidal Swamp Schemes that Land Units are not only based on soil characteristics. They must include the topography of the land related to the water levels in the adjoining canals throughout the scheme at high tide and mean tide. Predictions of water levels in new or upgraded canals and the expected future subsidence of the land should be included in the land characteristics for proper evaluation! Soil characteristics say little about the potentials of the land. Often soils with the pyrite layer at shallow depth are classified as non-suitable or marginal suitable. In reality you may find the best rice crops on these soils. It almost completely depends on the potential for leaching/percolation, that can be applied, to classify an acid sulphate soil as very suitable, suitable or marginal suitable for rice. See WebPages Thesis and Yields
Monitoring. In the O&M Model areas, the daily rainfall and the daily operation of the gates is recorded and its effects on water levels and water quality in open water and in the groundwater. Processed and updated data are shown in graphs and are connected by hotlinks on Thematic maps with gate control structures or representative locations within the O&M Model areas. The system provides a management tool at Central Level by comparing objectives with actual results in gate operation and if targeted outputs are proceeding according plan. See Leaching/Rainfall graph as an example.