water Article Observed Trends of Climate and River Discharge in Mongolia’s Selenga Sub-Basin of the Lake Baikal Basin Batsuren Dorjsuren 1,2 , Denghua Yan 1,3,4,*, Hao Wang 1,3,4, Sonomdagva Chonokhuu 2 , Altanbold Enkhbold 5, Xu Yiran 6, Abel Girma 1,7 , Mohammed Gedefaw 1,7 and Asaminew Abiyu 1 1 College of Environmental Science and Engineering, Donghua University, Shanghai 201620, China; [email protected] (B.D.); [email protected] (H.W.); [email protected] (A.G.); [email protected] (M.G.); [email protected] (A.A.) 2 Department of Environment and Forest Engineering, School of Engineering and Applied Sciences, National University of Mongolia, Ulaanbaatar 210646, Mongolia; [email protected] 3 State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin, China Institute of Water Resources and Hydropower Research (IWHR), Beijing 100038, China 4 Water Resources Department, China Institute of Water Resources and Hydropower Research (IWHR), Beijing 100038, China 5 Department of Geography, School of Art & Sciences, National University of Mongolia, Ulaanbaatar 210646, Mongolia; [email protected] 6 School of Resources and Earth Science, China University of Mining and Technology, Xuzhou 221116, China; [email protected] 7 Department of Natural Resource Management, University of Gondar, Gondar 196, Ethiopia * Correspondence: [email protected]; Tel.: +86-10-68781976 Received: 11 September 2018; Accepted: 9 October 2018; Published: 12 October 2018 Abstract: Mongolia’s Selenga sub-basin of the Lake Baikal basin is spatially extensive, with pronounced environmental gradients driven primarily by precipitation and air temperature on broad scales. Therefore, it is an ideal region to examine the dynamics of the climate and the hydrological system. This study investigated the annual precipitation, air temperature, and river discharge variability at five selected stations of the sub-basin by using Mann-Kendall (MK), Innovative trend analysis method (ITAM), and Sen’s slope estimator test. The result showed that the trend of annual precipitation was slightly increasing in Ulaanbaatar (Z = 0.71), Erdenet (Z = 0.13), and Tsetserleg (Z = 0.26) stations. Whereas Murun (Z = 2.45) and Sukhbaatar (Z = 1.06) stations showed a significant increasing trend. And also, the trend of annual air temperature in Ulaanbaatar (Z = 5.88), Erdenet (Z = 3.87), Tsetserleg (Z = 4.38), Murun (Z = 4.77), and Sukhbaatar (Z = 2.85) was sharply increased. The average air temperature has significantly increased by 1.4 ◦C in the past 38 years. This is very high in the semi-arid zone of central Asia. The river discharge showed a significantly decreasing trend during the study period years. It has been apparent since 1995. The findings of this paper could help researchers to understand the annual variability of precipitation, air temperature, and river discharge over the study region and, therefore, become a foundation for further studies. Keywords: precipitation; air temperature; river discharge; Mann-Kendall test; Selenga river basin; Lake Baikal basin; Mongolia 1. Introduction The Lake Baikal basin (LBB) is a suitable area to study climate change impacts. The climate is a long-term prevailing weather condition. Weather parameters include air temperature, precipitation, Water 2018, 10, 1436; doi:10.3390/w10101436 www.mdpi.com/journal/water Water 2018, 10, 1436 2 of 18 humidity, sunshine hours, cloudiness, atmospheric pressure, the number of rainy days, wind velocity, etc. These parameters interact directly or indirectly, greatly affecting the environment and the living organisms [1]. The semi-arid environment is highly vulnerable to climate change [2,3]. Land surface temperature is an important ecological factor and its warming trend will influence the topsoil [4,5]. Evapotranspiration and precipitation rates may change due to changes in soil temperature and air temperature. Precipitation change may greatly affect the hydrological system of the basin. Due to climate change and intensive human activities in recent decades, the runoff of many rivers in the world has been changing. About 22% of the world’s rivers were shown to have a significant decrease in the annual runoff because of increasing water consumptions and diversion [6,7]. The most sensitive areas for climate change are arid and semi-arid regions of central Asia [2,8,9]. LBB is the largest representative of these regions [3,10]. Lake Baikal, as the world’s largest natural freshwater lake and its corresponding catchments, is already affected by climate change and the water quantity becomes erratic [10]. In recent decades, changes in hydrological and water quantity are primarily attributed to climate change, land use change, contaminant influx from mining areas and urban settlements as well [11]. As the largest sub-basin of LBB, Selenga River basin is located in the Mongolian and Russian Federation. The Mongolian plateau is spatially extensive, with pronounced environmental gradients driven primarily by precipitation and air temperature on large scales. Therefore, it is an ideal region to examine the dynamics of the landscape structures and hydrology parameters [9]. This area, hydro-climatic changes can also lead to a shift in hydrology parameters, ecosystem and lake conditions in these areas. In addition, human activity effects on water pollution, water resources, sedimentary, and river discharge. In particular, in the Mongolian’s Selenga River basin high socio-economic activities are taking place. In the study region, there is high population density particularly, around Tuul and Kharaa sub basin. The sub basin is located in the biggest cities of Mongolia (Ulaanbaatar, Darkhan, and Erdenet), thus the river basin is highly consumed by the city residence. They consumed the water for agriculture, recreation and domestic use. In addition, the Selenga river basin water resource is used by the mining industry. Thus, it has a great role in reducing the quantity of the basin water flow [3,11,12]. This paper aims to investigate spatial and temporal changes in climate and river discharge changes in Mongolia’s Selenga sub-basin of the LBB understanding from 1979 to 2016. The overall objectives of the present study are (i) to identify historical climate trends, (ii) to identify trends of spatial and temporal changes in the river discharge, (iii) to assess the relationship and to which extent can climate change trends affect the river discharge. 2. Materials and Methods 2.1. Study Area Lake Baikal is the oldest (about 25 million years old), deepest (1637 m) and largest freshwater lake (23,000 km3) and is located in the southern part of East Siberia [13]. The transboundary basin of Lake Baikal is located on the boundary of North and Central Asia (96◦520–113◦500 N, 46◦280–56◦420 W) [12]. The longest stretch of the basin from southwest to north-east is 1470 km, and from west to east is 962 km. The minimal length from west to east is 193 km (Figure1). The total area of the basin is 573,478 km 2, and 52% of which belong to Mongolia and the remaining belongs to the Russian Federation [14]. In recognition of its biodiversity and endemism, United Nations Educational, Scientific and Cultural Organization (UNESCO) declared Lake Baikal as a World Heritage Site in 1996. The lake contains an outstanding variety of endemic flora and fauna, which is an exceptional value to evolutionary science. It is also surrounded by a system of protected areas with good scenery and natural values [10,15,16]. As the largest sub-basin of LBB, Selenga River basin is located in the Mongolian and Russian Federation. The Selenga is a Trans-boundary river, the largest tributary of Lake Baikal. On the average, it discharges into Lake Baikal ~30 km3 of water, i.e., half of the total inflow into the lake. Water 2018, 10, 1436 3 of 18 Water 2018, 10, x FOR PEER REVIEW 3 of 3 Forty-six percent of Selenga annualannual runoff forms in Mongolian territory.territory. The Mongolian plateau is spatially extensive, with pronounced environmenta environmentall gradients driven primarily by precipitation and air temperaturetemperature on on large large scales. scales. The The length length of the of riverthe river is 1024 is km,1024 its km, drainage its drainage area is 447.06 area thousandis 447.06 2 2 thousandkm , of which km2, 148.06of which thousand 148.06 thousand km are in km the2 are territory in the ofterritory Russia. of Russia. Figure 1. Location of Lake Baikal basin (LBB), Water ga gaugeuge station and meteorological stations of the Selenga River basin locatedlocated in the Mongolian. 2.2. Data Sources The datadata ofof air air temperature, temperature, precipitation precipitation and and hydrologic hydrologic data data of in of Mongolia’s in Mongolia’s Selenga Selenga river basinriver werebasin takenwere fromtaken Information from Information and Research and InstituteResearch of Institute Meteorology, of Meteorology, Hydrology, andHydrology, Environment and (IRIMHE)Environment hosts (IRIMHE) (http://irimhe.namem.gov.mn/ hosts (http://irimhe.), andnamem.gov.mn/), National Centers and for Environmental National Centers Information for EnvironmentalNOAA’s National Information Centers for NOAA’s Environmental National InformationCenters for Environmental (NCEI) hosts ( https://ngdc.noaa.gov/Information (NCEI) hosts). The(https://ngdc.noaa.gov/). location of the 5 water The gauge location stations of the used 5 inwater this gauge study isstations shown used in Figure in this1. For study the is selection shown ofin Figureclimate 1. and For waterthe selection gauge stationsof climate in and Mongolia’s water gauge Selenga stations sub-basin in Mongolia’s of the LBB, Selenga the following sub-basin factors of the wereLBB, takenthe following into consideration: factors were (1) spatialtaken distribution;into consider (2)ation: capacity (1) spatial of stations distri andbution; (3) whether (2) capacity it is near of stationsto the water and system(3) whether (Figure it is1)[ near8,17 to]. the water system (Figure 1) [8,17].