Impacts of climate change on groundwater recharge in Kucuk Menderes River Basin in Western Turkey

Groundwater is an important component of the global freshwater supply and is affected by climate. There is a strong need to understand and evaluate the impacts of climate change over the long term, in order to better plan and manage precious groundwater resources. Turkey, located in Mediterranean basin, is threatened by climate change. The purpose of this study was, through a quantitative overview, to determine the impacts of climate change on the groundwater recharge rates in Kucuk Menderes River Basin in western Turkey. According to the data of odemi and Selcuk meteorological stations located in the basin, there is a significantly decreasing trend in precipitation combined with increasing trends in temperature and evaporation observed in 1964-2011. The calculations of groundwater recharge with hydrologic budget method for the observation period showed an approximately 15\% decline in groundwater recharge in the basin. Thus, the combined impacts of climate change and excessive groundwater pumping, due to increasing water demand, have caused a significant decline in groundwater levels. Consequently, the proper management of the groundwater resources threatened by climate change requires effective governance to both mitigate the adverse impacts of climate change and facilitate the adaptation of sustainable integrated water management policies

Sustainable management of Mogan and Eymir Lakes in Central Turkey

Mogan and Eymir Lakes, located 20 km south of Ankara in Central Turkey, are important aesthetic, recreational, and ecological resources. Dikilitas and Ikizce reservoirs, constructed on upstream surface waters, are two man-made structures in the basin encompassing an area of 985 km(2). The purpose of this study is to quantify groundwater components in lakes' budgets and to assess the potential impacts of upstream reservoirs on lake levels for sustainable management of the system. Available data have been used to develop a conceptual model of the system. A three-dimensional groundwater model, incorporating a lake component, has been developed for the system. The model has been calibrated successfully under transient conditions over a period of 6 years using monthly periods. The results show that groundwater inflows and outflows have the lowest contribution to the overall lakes' budget. The model has been subsequently used to evaluate the impacts of upstream reservoirs. The results show that these reservoirs have a significant effect on lake stages but not on groundwater levels. A trade-off curve between the quantum of water released and the average stage in Lake Mogan has been developed to enhance decision makers' ability for sustainable management of the system in the long term

Assessing the impact of climate change on Mogan and Eymir Lakes' levels in Central Turkey

Global warming is likely to have significant effect on the hydrological cycle. Some parts of the world may see significant reductions in precipitation or major alterations in the timing of wet and dry seasons. Climate change is one of the serious pressures facing water resources and their management over the next few years and decades. As part of the southern belt of Mediterranean Europe, Turkey is highly vulnerable to anticipated climate change impacts. The changes in global climate will seriously affect inland freshwater ecosystems and coastal lakes. Mogan and Eymir Lakes located in Central Turkey are shallow lakes that may be impacted significantly by climate change. The interaction between the lakes and groundwater system has been modelled in order to analyse the response of lake levels to climate change over a planning period of 96 years, beginning from October 2004 and ending in September 2100. The impacts of the emission scenarios of A2 and B1 of the Intergovernmental Panel on Climate Change (IPCC) on lake levels have been analyzed with the help of the lake-aquifer simulation model. The fluctuations in lake levels due to climate change scenarios are compared with the results of a scenario generated by the assumption of the continuation of the average recharge and discharge conditions observed for 1999 and 2004. The results show that very small, but long-term changes to precipitation and temperature have the potential to cause significant declines in lake levels and temporary drying of the lakes in the long-term. The impact of climate change on lake levels will depend on how these water resources are managed in the future

Impacts of climatic variables on water-level variations in two shallow Eastern Mediterranean lakes

Variations in temperature and precipitation have direct impacts on the physical, chemical and biological characteristics of the shallow lakes. This paper examines the possible linkages between climate variables and the water levels of shallow interconnected Lakes Mogan and Eymir, located 20 km south of Ankara in Central Anatolia. The variations in the lakes' water levels during 1996-2015 are studied and the impacts of climate variables on the lake levels are assessed to address the long-term consequences. The nonparametric Mann-Kendall test was used to quantify trends in the climate variables and the lakes' level fluctuations between the observation periods 1998-2007 and 2008-2014. Statistical analyses results showed that precipitation and temperature have crucial influence on the variations in the lakes' levels. The projected increase in temperature and decrease in precipitation over the next century may produce substantial decreases in lake levels, with consequent drying of both lakes

Assessing the impacts of climate change on sustainable management of coastal aquifers

Water is a vital resource for the survival of not only human population, but also almost all ecosystems. Constituting 30 % of all freshwater, groundwater is the main source of available freshwater. Coastal aquifers, which serve as the major freshwater source for densely populated zones, are of vital importance and quite vulnerable to climate change. This paper examines the significant consequences of climate change, decreasing recharge rates, sea-level rise and increasing freshwater demand on the sustainable management of coastal aquifers, via a hypothetical case study. A 3-D numerical model is developed using SEAWAT, to simulate a circular island aquifer in the form of a freshwater lens surrounded by saltwater. Issues such as sloping land surface resulting in landward migration of the coastal boundary and transient response of the system due to pumping are considered through a set of predictive simulations. To assess the sensitivity of the model results to important parameters, a sensitivity analysis is performed. Results of this research, revealing the effects of mentioned pressures on the long-term sustainability of the freshwater resource, are evaluated on the basis of groundwater reserves and intrusion of the freshwater-saltwater interface in lateral and vertical directions. These outcomes are further used to determine the sustainable pumping rate of the system, considering both quantity and quality of the groundwater resources

Trend Analyses of Meteorological Variables and Lake Levels for Two Shallow Lakes in Central Turkey

Trend analyses of meteorological variables play an important role in assessing the long-term changes in water levels for sustainable management of shallow lakes that are extremely vulnerable to climatic variations. Lake Mogan and Lake Eymir are shallow lakes offering aesthetic, recreational, and ecological resources. Trend analyses of monthly water levels and meteorological variables affecting lake levels were done by the Mann-Kendall (MK), Modified Mann-Kendall (MMK), Sen Trend (ST), and Linear trend (LT) methods. Trend analyses of monthly lake levels for both lakes revealed an increasing trend with the Mann-Kendall, Linear, and Sen Trend tests. The Modified Mann-Kendall test results were statistically significant with an increasing trend for Eymir lake levels, but they were insignificant for Mogan lake due to the presence of autocorrelation. While trend analyses of meteorological variables by Sen Test were significant at all tested variables and confidence levels, Mann-Kendall, Modified Mann-Kendall, and Linear trend provided significant trends for only humidity and wind speed. The trend analyses of Sen Test gave increasing trends for temperature, wind speed, cloud cover, and precipitation; and decreasing trends for humidity, sunshine duration, and pan evaporation. These results show that increasing precipitation and decreasing pan evaporation resulted in increasing lake levels. The results further demonstrated an inverse relationship between the trends of air temperature and pan evaporation, pointing to an apparent ``Evaporation Paradox{''}, also observed in other locations. However, the increased cloud cover happens to offset the effects of increased temperature and decreased humidity on pan evaporation. Thus, all relevant factors affecting pan evaporation should be considered to explain seemingly paradoxical observations

Trend Analyses of Meteorological Variables and Lake Levels for Two Shallow Lakes in Central Turkey

Trend analyses of meteorological variables play an important role in assessing the long-term changes in water levels for sustainable management of shallow lakes that are extremely vulnerable to climatic variations. Lake Mogan and Lake Eymir are shallow lakes offering aesthetic, recreational, and ecological resources. Trend analyses of monthly water levels and meteorological variables affecting lake levels were done by the Mann-Kendall (MK), Modified Mann-Kendall (MMK), Sen Trend (ST), and Linear trend (LT) methods. Trend analyses of monthly lake levels for both lakes revealed an increasing trend with the Mann-Kendall, Linear, and Sen Trend tests. The Modified Mann-Kendall test results were statistically significant with an increasing trend for Eymir lake levels, but they were insignificant for Mogan lake due to the presence of autocorrelation. While trend analyses of meteorological variables by Sen Test were significant at all tested variables and confidence levels, Mann-Kendall, Modified Mann-Kendall, and Linear trend provided significant trends for only humidity and wind speed. The trend analyses of Sen Test gave increasing trends for temperature, wind speed, cloud cover, and precipitation; and decreasing trends for humidity, sunshine duration, and pan evaporation. These results show that increasing precipitation and decreasing pan evaporation resulted in increasing lake levels. The results further demonstrated an inverse relationship between the trends of air temperature and pan evaporation, pointing to an apparent “Evaporation Paradox”, also observed in other locations. However, the increased cloud cover happens to offset the effects of increased temperature and decreased humidity on pan evaporation. Thus, all relevant factors affecting pan evaporation should be considered to explain seemingly paradoxical observations

Impacts of Decreasing Recharge Rates on Sustainable Groundwater Management

Groundwater is a vital resource for living and food security for at least two billion people worldwide. Ever increasing demand on groundwater has led to overexploitation of the aquifers and degradation of groundwater quality. Climate change will exacerbate these problems by producing reduced recharge rates in some areas, more reliance on groundwater resources due to decrease in reliability of surface waters, farther inland penetration of saltwater intrusion in response to both sea-level rise and excessive groundwater extraction and deterioration of groundwater quality by increased flushing of urban and agricultural waste due to more frequent flooding. These problems emerged the concern about the sustainable management of groundwater so that it is not depleted while the increasing demand is satisfied under the pressures exerted by the climate change. This paper examines one of the most significant consequences of climate change, decreasing recharge rates, on the sustainable management of groundwater resources using a hypothetical case stud

Impacts of climatic variables on water-level variations in two shallow Eastern Mediterranean lakes

Variations in temperature and precipitation have direct impacts on the physical, chemical and biological characteristics of the shallow lakes. This paper examines the possible linkages between climate variables and the water levels of shallow interconnected Lakes Mogan and Eymir, located 20 km south of Ankara in Central Anatolia. The variations in the lakes' water levels during 1996-2015 are studied and the impacts of climate variables on the lake levels are assessed to address the long-term consequences. The nonparametric Mann-Kendall test was used to quantify trends in the climate variables and the lakes' level fluctuations between the observation periods 1998-2007 and 2008-2014. Statistical analyses results showed that precipitation and temperature have crucial influence on the variations in the lakes' levels. The projected increase in temperature and decrease in precipitation over the next century may produce substantial decreases in lake levels, with consequent drying of both lakes