Strategic analysis of the drought resilience of water supply systems

Severe droughts can result in shortages of water supplies, with widespread social and economic consequences. Here we use a coupled simulation model to assess the reliability of public water supplies in England, in the context of changing scenarios of water demand, water regulation and climate change. The coupled simulation model combines climate simulations, a national-scale hydrological model and a national-scale water resource systems model to demonstrate how extreme meteorological droughts translate into hydrological droughts and water shortages for water users. We use this model to explore the effectiveness of strategic water resource options that are being planned in England to secure water supplies to most of England's population up to a drought return period of 1 in 500 years. We conclude that it is possible to achieve a 1-in-500-years standard in locations where strategic resource options are used, while also reducing water abstraction to restore the aquatic environment. However, the target will be easier to achieve if effective steps are also taken to reduce water demand. This article is part of the Royal Society Science+ meeting issue ‘Drought risk in the Anthropocene’

Estimation of Blue and Green Water Potentials of Türkiye under Global Climate Change Effects

This study analyzed the impact of global climate change scenarios on the water resources of Turkiye by means of various climate and hydrological simulations projected for this century. An integrated approach was used by coupling regional climate models and a semi-distributed hydrologic model to assess the climate change impacts. A regional climate model, that is the output of 3 global models (HadGEM2-ES, MPI-ESM-MR and CNRM-CM5.1), has been conducted with RCP4.5 & RCP8.5 emission scenarios for whole the country at the watershed-scale with a resolution of 10x10 km. Hydrological simulations were conducted by using the Soil and Water Assessment Tool (SWAT) Model to determine the variation of surface and groundwater resources based on climate change projections. Blue water flow (water yield + deep aquifer recharges), green water storage (soil water), and water surplus/deficit projections have been conducted considering the current and projected status for water-consuming sectors of domestic, industry, agriculture, and ecosystem services. Results attained were further evaluated through statistical methods regarding blue water flow and green water storage potential of the country. The main purpose of the study was to aid the legal authorities, and decision-makers in prioritizing the environmental measures to be taken for mitigation of climate change impacts on Turkiye in the long- run. The work was the first country-wide hydrological modelling study through globally accepted climate change scenarios

MODEL SUPPORTED HYDROLOGICAL ANALYSIS OF DARLIK CREEK WATERSHED, ISTANBUL TURKEY

Istanbul, which is the most crowded city of Turkey, is also among the world's highly populated cities, and its population is increasing day by day so that water resources of this metropolitan are under excessive stress. Today, population of this huge metropolitan is about 13,500,000 and this mega city needs approximately 2,250,000 m(3) water per day. Considerable amount of this demand -almost allis supplied from the dams around the city and by inter-basin water transfer

Accounting for the water related ecosystem services of forests in the Southern Aegean region of Turkey

This study aims to model hydrological ecosystem services provided by forests and explore how they can be captured in an ecosystem accounting framework. We test a dynamic GIS-based hydrological model to quantify and map key hydrological ecosystem services in the Southern Aegean Region of Turkey and integrate the services into an ecosystem account following the System of Environmental Economic Accounting – Ecosystem Accounting (SEEA EA). We map and account for services in physical and monetary terms, using an innovative model to quantify flood control services. Our paper connects forest management with water resource supply, eliciting the hydrological role of forests. The combined value of the three ecological services (groundwater recharge, flood control and sediment control) is about 201 million €/year. Reduction in forest coverage means that the economy will face the consequences of losses of these critical regulating services. Finally, we discuss opportunities, challenges, and limitations in the practical application of the ecosystem accounting concept

Assessing the Water-Resources Potential of Istanbul by Using a Soil and Water Assessment Tool (SWAT) Hydrological Model

Uncertainties due to climate change and population growth have created a critical situation for many megacities. Investigating spatio-temporal variability of water resources is, therefore, a critical initial step for water-resource management. This paper is a first study on the evaluation of water-budget components of water resources in Istanbul using a high-resolution hydrological model. In this work, the water resources of Istanbul and surrounding watersheds were modeled using the Soil and Water Assessment Tool (SWAT), which is a continuous-time, semi-distributed, process-based model. The SWAT-CUP program was used for calibration/validation of the model with uncertainty analysis using the SUFI-2 algorithm over the period 1977–2013 at 25 gauge stations. The results reveal that the annual blue-water potential of Istanbul is 3.5 billion m3, whereas the green-water flow and storage are 2.9 billion m3 and 0.7 billion m3, respectively. Watersheds located on the Asian side of the Istanbul megacity yield more blue-water resources compared to the European side, and constitute 75% of the total potential water resources. The model highlights the water potential of the city under current circumstances and gives an insight into its spatial distribution over the region. This study provides a strong basis for forthcoming studies concerning better water-resources management practices, climate change and water-quality studies, as well as other socio-economic scenario analyses in the region

Impacts of Land Cover/Use Changes on Hydrological Processes in a Rapidly Urbanizing Mid-latitude Water Supply Catchment

This research aimed to evaluate the impact of land cover/use changes on watershed responses and hydrological processes by applying the Soil and Water Assessment Tool (SWAT) distributed hydrologic model to the Buyukcekmece Water Basin of Istanbul Metropolitan city. SWAT model was run for two different scenarios for the 40-year period between 1973 and 2012, after completing calibration procedures under gauge-data scarce conditions. For the first scenario, 1990 dated Land cover/land use (LCLU) map and meteorological data obtained between 1973 and 2012 were used. For the second scenario, 2006 dated LCLU map and same meteorological data were used to analyze the impact of changing landscape characteristics on hydrological processes. In the selected watershed, LCLU changes started towards the end of the 1980s and reached a significant status in 2006; therefore, 1990 and 2006 dated LCLU maps are important to model human impact period in the watershed. Afterwards, LCLU changes within sub-basin level were investigated to quantify the effects of different types of land changes on the major hydrological components such as actual evapotranspiration, percolation, soil water, base flow, surface runoff and runoff. Our analysis indicated that, under the same climatic conditions, changes in land cover/use, specifically urbanization, played a considerable role in hydrological dynamics with changes on actual transpiration, base flow, surface runoff, runoff, percolation and soil water mainly due to urban and agricultural area changes. Among the different hydrological components analyzed at watershed level, percolation, ET and base flow were found to be highly sensitive to LCLU changes, whereas soil water was found as the least sensitive to same LCLU changes