Project

Problem

The Casamance river has a long estuary that consists of a large system of meandering creeks and mangrove forest. In the dry season the river can be saline till 250 kilometers upstream. In this period salinities twice as much as the ocean can occur, caused by evaporation and insignificant discharge. During the seventies and eighties, there was a lack of precipitation in the Casamance catchment. As a result the river became more saline and less agriculture was possible. Because of this, people in the region started to migrate from the river. Now, with less manpower in the region, it’s harder to maintain the dikes around the rice paddies, the major form of agriculture. Lack of maintenance causes saline erosion. A second factor that might cause higher salinities and dike breaches as well is the logging of mangrove forests. This reduces the natural friction in the estuary, causing the tidal motion to strengthen.

Goal

The goal of the project is to improve the agriculture in the region, by managing the river and the paddies. On the long term an increase of salt intrusion has to be prevented, therefore good understanding of the salt intrusion, the tidal movement and the hydrological situation are needed. If there are parameters which are affecting the salinity significant, which can be influenced by river policy, for instance the friction, this has to be advised. On short term there may be possibilities to improve agriculture with a mitigating approach. Given the salt intrusion and tidal regime, improvements might be found in changing the land use in time or place, changing the amounts of crops, changing the irrigation schedule, the inlet structure itself.

Approach

The first part of the project will consist of modelling the salt intrusion and the tidal movement in the river, and gathering information on precipitation, evaporation, runoff etc. With this information the salt intrusion and the tidal movement can be understood and predicted. With this information, long term advice can be given for the river basin. In the second part of the project the focus will be on short term measures on a small scale, after understanding of the local land use practices and with help of the gathered information. These measures can then be tested and will be informed to the local community.