Effect of Protection Level in the Hydroperiod of Water Bodies on Doñana’s Aeolian Sands

Javier Bustamante,Isabel Afán,David Aragonés

doi:10.3390/rs8100867

Abstract

Mediterranean temporary ponds on Doñana’s aeolian sands form an extensive system of small dynamic water bodies, dependent on precipitation and groundwater, of considerable importance for biodiversity conservation. Different areas of the aeolian sands have received different levels of environmental protection since 1969, and this has influenced the degree of conservation and the flooding dynamic of these temporary surface waters. We use the Landsat series of satellite images from 1985 to 2014 to study the temporal dynamic of small temporary water bodies on the aeolian sands in relation to the protection level and to distance to water abstraction pressures from agriculture and residential areas. The results show that even with small and ephemeral water bodies optical remote sensing time-series are an effective way to study their flooding temporal dynamics. The protected areas of the aeolian sands hold a better preserved system of temporary ponds, with a flooding dynamic that fluctuates with precipitation. The unprotected area shows an increase in mean hydroperiod duration, and surface flooded, and a decline in hydroperiod variability. This seems to be due to the creation of irrigation ponds and the artificialization of the flooding regime of the natural temporary ponds, that either receive excess irrigation water or dry-up due to the lowering of the groundwater table level. Although a decline in hydroperiod duration of temporary ponds is seen as negative to the system, an increase in hydroperiod of surface waters due to artificialization, or a decline in variability cannot be considered as positive compensatory effects.

Highlights

The Doñana National Park holds a system of ponds on aeolian sands that is considered one of the best examples of Mediterranean temporary ponds in Europe [1,2]
Our study shows that it is possible to study the long-term flooding dynamic of a system of small temporary ponds using the Landsat satellites time-series of optical images to evaluate the effect of protection level, and the threats caused by water abstraction by irrigation cultures and residential areas
The results indicate that the protected area holds a better preserved system of temporary ponds but that its flooding dynamic seems to be affected by water abstraction by irrigated cultures and, to a smaller extent, by residential areas

Summary

Introduction

The Doñana National Park holds a system of ponds on aeolian sands that is considered one of the best examples of Mediterranean temporary ponds in Europe [1,2]. Ponds differ in size and in the length of time they get flooded every year They go from rain puddles that remain flooded for a few days -or weeks on rainy winters- to some ponds, up to 187 ha in size, that keep permanent water in part of their basin most of the years. We denominate hydroperiod the duration of the flooding period of a pond in an annual cycle [5]. This is an important ecological parameter as it determines which plants and animals can use the pond for breeding and to complete their life cycles [2].

Methods

Results

Discussion

Conclusion