Integrated water management scenarios for wetland protection: application in Trichonis Lake

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Abstract

Sustainable water resources management is a priority issue today, since it can contribute to achieving both environmental preservation and economic prosperity. Wetlands constitute a significant environmental system, since they incorporate unique habitats with endemic and migrant species and therefore contribute to the conservation of high global biodiversity. However, they suffer from degradation because of the intensification of agriculture, the increase in pollution rates and poor water management practices. This study attempts to develop a methodology by combining GIS applications, remote-sensing techniques and physically based hydrologic modelling for the formation of water management plans in lake catchments. This methodology has been tested in Trichonis Lake catchment, in Western Greece, where the endangered calcareous fens habitat undergoes great ecological stresses due to the irrational use of local water resources. The first results indicated that the particular methodology operated efficiently. The suggested scenario has been adopted by the local water authorities and the significant water level fluctuations observed in the past have been eliminated to approximately 25% in the initial implementation period.

Introduction

Developing sustainable water management plans that incorporate both environmental and socio-economic perspectives is a difficult but essential task in order to prevent potential environmental deterioration and enhance economic growth. Human-induced activities and land use alterations often comprise significant disturbances for water resources and aquatic ecosystems. These disturbances may reach intensities that rival the most severe natural disturbances (Turner et al., 1993). Non-rational management of water resources causes lowering of ground water levels in wetland areas, resulting in unseasonably dry conditions that may lead to environmental degradation (Mitsch and Gosselink, 1993). Wetlands are multifunctional and dynamic systems that incorporate very specific hydrologic and ecological conditions. They provide important services, such as purification and regulation of water flows, numerous resources for human uses, habitats for plants, animals and micro-organisms and recreational opportunities. However, during the last century, intensification of agriculture, unsustainable water uses, an increase in pollution rates and climatic changes have put significant stresses on wetlands and have caused their progressive degradation. An increasing need for implementing sustainable water management plans has emerged. Such an effort may result in covering both human-induced and ecological-related water needs, as well as in preserving high quality and quantity storages. Several scientific efforts in developing decision support systems to facilitate wetlands management have been observed during the last decade with special focus on assessing impacts from human interventions on the hydrologic regime of wetland areas (Quinn and Hanna, 2003, Kuper et al., 2003). This study attempts to depict the hydrologic modelling contribution in developing an adaptive water management plan, which takes into consideration both economic development and environmental health. In the basin of Trichonis Lake (Western Greece) the ecologically significant and priority habitat of calcareous fens (Natura 2000 network) has been degraded during the last 40 years due to the high water level fluctuations, caused mainly by unsustainable use of water resources. The implementation of the management plan developed here will offer favourable and stable hydrologic conditions for the area's wetlands, facilitate environmental restoration and achieve long-term water sufficiency for anthropogenic activities. For this purpose GIS technologies, hydrologic models and remote sensing techniques have been combined to enhance the water management scenario formation process and a relevant methodology has been illustrated that can be widely applicable to similar catchments.

The study area is Trichonis Lake catchment, a 399 km2 semi-mountainous area in Western Greece (Fig. 1). This region incorporates significant water resources, since it includes a large and deep freshwater body, Trichonis Lake, which has a surface area of 97 km2, a maximum depth of 58 m and a potential water volume of approximately 2.8×109 m3 (Dimitriou et al., 2001). The regional climate is characterized as semi-arid to arid Mediterranean with an average annual rainfall of 936 mm and an average annual temperature of 17 °C which fluctuates by 19 °C annually.

The high availability of water contributes to the formation of extended wetlands around the lake. A variety of ecologically significant habitats such as calcareous fens with Cladium mariscus and Carex sp. are present. Under EU legislation (Habitats Directive, Annex I), calcareous fens are a priority, protected habitat. This habitat type is usually encountered in lowlands close to water bodies and in areas where the water table is very close to the ground surface, since its growth requires high soil moisture conditions (Georgiadis et al., 2000).

The geology of the catchment is complex as it is intensely tectonized and comprises many different rock formations with a variety of hydrogeologic properties. In particular, medium weathered, fissured limestone, which has relatively high infiltration rates, covers a great proportion of the catchment (31% of the total area). Flysch formations also have a significant surficial extent in the basin (30% of the catchment) and contain sandstones and clayey schists, which can be characterized as low permeability formations (Fig. 1). Quaternary and pleistocenic sediments greatly affect the local hydrologic regime, since they cover 31% of the catchment extent and facilitate the occurrence of local underground water storages due to their low to medium permeability (Fig. 1).

Section snippets

Materials and methods

The formulation of a sustainable water management plan involves a multidisciplinary scientific approach and profound study of the area's characteristics (hydrologic, geologic, socio-economic, etc.).

Estimating specific catchment hydrologic properties is a difficult scientific task, requiring good comprehension of the particular water system, profound knowledge of the geologic and geomorphologic conditions and full series of relevant data. Sophisticated physically based hydrologic modelling was

Application to Trichonis Lake catchment

The MIKE SHE result file after a post-process provided the catchment's water budget components. Thus, rainfall for the simulated period (1998–1999) reached 1337 mm, while actual evapotranspiration was estimated to be 798 mm (approximately 59% of the rainfall, Fig. 4). This increased amount of evapotranspiration is expected since the lake has a large open water surface and temperatures are quite high as well (average annual temperature: 17.25 °C).

The water quantity stored on the ground surface,

Concluding remarks

Designing and implementing sustainable water management plans can provide solutions to water deficiency problems. However, this is not an easy task since it requires a multidisciplinary approach and an effective tackling of numerous problems that may arise. Understanding natural disturbance regimes on the environment and eliminating the new forthcoming nuisances from human interventions are crucial foundations for designing management systems (Nakamura et al., 2000). Further, the use of

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