Case Study Atankwidi Catchment (Westafrica, Volta Basin)

real gauge (No.1) fictive gauge (No.2) fictive gauge (No.3) Fictive irrigation field N km0 3 2 Subcatcment 3 Subcatchment 2 & implemented fictive reservoir Subcatchment 1 Study Area: Atankwidi Catchment (Volta Basin)

Example of the model application: Reservoir volume: m³ Reservoir area:81701 m² Irrigation system command area:50 ha Maximum number of iterations:4 Area maxArea minOptimization Value Wet Rice1513 Dry Rice1012 Tomato1012 Onion1513

Red Line Constraint: Reservoir Volume>1000 m³ Constraints not fullfilled Reduction of the irrigated area Increase of the Reservoire Volume

Results

Reduction of the Irrigation Field Area

Reduction of water withdrawal

OBSERVED VALUE = resVol month 1= min : | max : true month 2= min : | max : failed month 3= min : | max : failed month 4= min : | max : true month 5= min : | max : true month 6= min : | max : true month 7= min : | max : true month 8= min : | max : true month 9= min : | max : true month 10= min : | max : failed month 11= min : | max : failed month 12= min : | max : failed OBSERVED VALUE = resVol month 1= min : | max : true month 2= min : | max : failed month 3= min : | max : failed month 4= min : | max : true month 5= min : | max : failed17 times month 6=min : | max : true month 7= min : | max : true month 8= min : | max : true month 9= min : | max : true month 10= min : | max : failed month 11= min : | max : failed month 12= min : | max : failed Optimization: Reservoir Volume

GAMS: Agricultural Profit

Discussion … still many problems : in the actual WaSiM-ETH version concerning reservoirs and irrigation, i.e. not adapted for irrigation of big areas & no consideration of evaporation and percolation from the reservoir Optimzation only possible by reducing / expanding the irrigated area Reservoir size (semi-arid areas)