Dynamics and Uncertainty in Environmental and Natural
Resource Management Under Scarcity : The Case of Irrigation.
Christophe BONTEMPSyand Stéphane COUTUREz
May 11, 1999
The objective of this paper is to study the problem of management of irrigation water.
We analyse farmers' economic rules of tactical irrigation scheduling in a certain or uncertain
environment under water scarcity. The optimal plans depend on uncertain weather conditions
We develop a dynamic economic model of irrigation water applications under certain or un-
certain weather conditions and in the context of a limited total quantity of water. We program
this economic model, introducing the agronomic model EPIC, which is used to obtain informa-
tion on the crop yield. The model is used to explain the optimal irrigation management plan
of corn in the area of Toulouse (France). This model improves water management and leads
to substantial reduction of water consumed. As an example, we show that the total quantity
of water needed for optimal irrigation scheduling in France is approximately a fourth of the
applications recommanded by agronomists.
Keywords : dynamic optimization, irrigation management, agroeconomic modeling, uncer-
The authors are grateful to Jean-Pierre Amigues, Pascal Favard, Jacky Puech, Maurice Cabelguenne, Philippe
Debaeke, and Nicole Bosc for their invaluable assistances during dierent stages of this study.
yINRA and LEERNA, Université de Toulouse I, 21 allée de Brienne, 31000 Toulouse, France. Email : bon-
zLEERNA and GREMAQ-UTI, Université de Toulouse I, 21 allée de Brienne, 31000 Toulouse, France. Email :
Many decision problems occur in a dynamic and uncertain framework. Optimization under un-
certainty is used in economics and nance when studying growth, investment, consumption and
portfolio allocation rules but also natural and environmental resources management. Several as-
pects of dynamic problems can be considered as