**5.2 Alternative water resources**

In cases of severe water scarcity, reducing water consumption may not be a remedy and thus searching for alternative water resources may become crucial.

Desalination of seawater or brackish water is considered as an important option of producing freshwater. Recent technologies and advances in the sector allow producing freshwater at affordable costs when higher amounts are intended. However, water withdrawals for desalination purposes may alter the well-being the related ecosystem. Thus, it is necessary to take into account the environmental impacts that might occur due to the planned water withdrawals. Also brine that is produced in desalination process should be properly disposed.

Another alternative source is reuse of treated wastewater. It is known that treated wastewater may be used for irrigating green land, parks and gardens in big cities. It can also be used for irrigating agricultural land if the national standards are satisfied in terms of irrigation water quality. Industries can also utilize treated wastewater in their processes providing that the quality of the goods manufactured remain unchanged (Asano et al., 2007).

Aquifers can be thought as storages where water loss through evaporation is relatively low. Thus, recharge of groundwater aquifers with treated wastewater is applied in different countries such as Israel and Spain (Esteban & Miguel, 2008; Salgot, 2008). However, it should be underlined that advanced treatment is necessary to protect the aquifers from pollution.

Another option is ecological sanitation (ECOSAN) practices. By such applications generated wastewater is separated into three streams at the source (yellow water, grey water and black water) that may be recycled after applying simpler treatment techniques. For example treated grey water may be used for irrigation and for recharge of aquifers. However, in most of the cases existing and usually old fashioned infrastructure is not compatible with ECOSAN. Reuse and/or disposal of each wastewater stream should be carefully planned. For example, yellow water could be used instead of fertilizer but if not desalinated salinity in human urine can harm the crops and the soil (Beler-Baykal et al., 2011).

#### **5.3 Inter-basin water transfer**

Szwed et al., (2010) states that water transfer from an area of relative abundance to an area of scarcity may smooth the spatial water variability. It is applied in many arid and semi-arid regions. Three points are important in water transfer: Feasibility regarding engineering works, hydrological conditions and ecological conditions of the basins. Pre-screening in terms of engineering works focus on costs of the work and on the length of water transmission lines. Besides, head loss/energy consumption of the pumps, natural and artificial barriers along the pipeline and its vicinity are also important factors to be considered.

Inter-basin water transfer depends on the availability of excess water from where the water is withdrawn. Especially the climatic conditions of both basins gain importance. If both basins face drought conditions in the same years, water transfer among them should not be considered as a feasible option. Both basins must be surveyed prior to realization of water transfer regarding their hydrological characteristics. During these surveys, long-term hydrological data must be analyzed. Watershed ecology is equally important. Socio-cultural conditions and economical characteristics should also be taken into consideration and sustainability should be kept in mind during water withdrawals. There are still contradicting opinions on inter-basin water transfer. They argue that inter-basin water transfer may no longer be viable in a future with climate change, as climate change stresses almost every source of freshwater. Also taking more water from the natural system has biological, ethical, and increasingly legal limitations (Karakaya and Gonenc, 2005; Hall et al., 2008). Consequently, it is advised to consider inter-basin water transfer to be considered as the last solution to water scarcity.
