| dc.description.abstracteng | Water is essential for life and for all human activities but also for preserving the environment and its resources. Rapidly growing population, intensification of agriculture, industrialization, urbanization, development of any kind and climatic factors are the main reasons for water pollution and scarcity conditions in many countries of the world (Tsihrintzis et al 2013, WWAP 2018).
1.1 Study region
The study region comprises the Mongolian part of the Selenga River Basin with a particular focus on the Kharaa, Tuul, Orkhon and their sub-basins, which are comparable with regard to the physical environment and socio-economic development (Karthe et al. 2013). The Selenga River itself has a transboundary catchment which is shared by two countries, Mongolia and Russia. Originating in Mongolia, it is the largest inflow of Lake Baikal with over 60 % of annual water amount contribution (UNOPS 2013). The delta of Selenga River is included in the list of Ramsar Wetlands of international importance because of its significant role as a habitat for flora and fauna as well as its role in functioning as a water filter against pollution flowing into Lake Baikal (UNOPS 2013). In Mongolia the Selenga River has a water catchment of 299,690 km2 (67 %) and is divided into six sub-basins, while the catchment area in Russia is about 147,370 km2 (33 %) (UNOPS 2013). The river plays an important role because 19 % of the total land area of Mongolia is located in its catchment, including the capital, important centers of industry and large farming areas (Nadmitov et al. 2015, Chalov et al. 2015).
The Tuul, Kharaa and Orkhon River Basins are home to Mongolia’s three largest cities (Ulaanbaatar, Darkhan and Erdenet, respectively) and to more than half of the country’s population. Moreover, the three river basins constitute important centers of agriculture, industry and mining (in particular for gold and copper). This does not only lead to a concentration of consumption but also of contamination risks. At the same time, water pollution in this region may harm a relatively large exposed population (Chalov et al. 2013).
The northern part of Mongolia is characterized by a highly continental climate with wide variations of annual, monthly and daily temperatures. The mean annual temperature is just below freezing, and annual precipitation ranges between 250-400 mm. Winters are long-lasting (monthly mean temperatures are 0°C or below between October and March) and very cold (temperatures frequently drop below -25°C), while summers are not only warm, but also the time of the main rainy period from June to August, when about 70 % of the annual precipitation falls (Hülsmann et al. 2015; Menzel et al. 2011).
Water availability is naturally limited due to low precipitation and high evaporation rates. Even though only 20% of the annual precipitation falls during the winter months, and sublimation losses are above 80%, the melting of snow and river icings produce a first considerable peak in river discharge around May (Minderlein & Menzel 2014). Because of a concentration of rainfall during the summer months, more than half of the annual runoff occurs during the months of July, August and September, albeit with a large interannual variability (Batimaa et al. 2005; Berezhnykh et al. 2012; Hülsmann et al. 2014). While open grasslands dominate low-lying regions, mountainous regions (particularly in the rivers’ headwater areas) are typically forested and play a key role in runoff formation (Menzel et al. 2011). | de |