Simulation model comparing the hydroperiod of temporary ponds with different shapes

A model of the water dynamics for shallow, small and temporary Mediterranean ponds has been developed taking into account the annual patterns of rainfall and potential evaporation, pond parameters (pond area, depth and shape) and watershed parameters (watershed area and saturated water content of the soil). This model predicts the amount of water retained in the pond in real time and therefore, when a pond is going to dry out. It is then possible to calculate how much water will remain in the pond after raining or the number of days per year that the pond is going to be dry. Analyses have been performed for different shapes of ponds and sensitivity of the state variables, at different values for the parameters. The most interesting result of our simulations is that the amount of water in the pond (as % of the total) strongly depends on pond shape and maximum depth and saturated water content of the watershed. Watershed area of the pond will only be important for low intensity rain regimes and for soils with very low saturated water content. Also, the number of days without water (per year) depends on shape and maximum pond depth. Deeper ponds will dry at a slower rate (and therefore have more days with water a year and consequently shorter drought periods) than shallower ones, independently of their area or the total amount of water. A conical pond should have more days with water for the same amount of rain, unless the pond does get totally full in each rainfall episode. Around the Mediterranean Basin, most temporary ponds have a certain degree of articiality (because of agriculture or farms). Thus, this model could help in controlling the hydroperiod by conveniently modifying shapes and depth of ponds to manage and preserve different species or biotic communities. The simulation model used is freely available from the authors or in: http://personales.upv.es/∼algarsal/temporary ponds.zip.