# Changes in Water Surface Area of the Lake in the Steppe Region of Mongolia: A Case Study of Ugii Nuur Lake, Central Mongolia

^{1}

^{2}

^{3}

^{4}

^{5}

^{6}

^{7}

^{*}

## Abstract

**:**

## 1. Introduction

^{2}. The main inflow of the lake is the Khogshin Orkhon river. The water regime of the lake was influenced by the flow regulating the capacity of the Orkhon river. Approximately 50% of the lake water surface area has a depth of lower than 3 m [11]. Several studies focused on lake sediments. Pagma et al. [17] determined the interrelation between lake physics and the surrounding climate by taking samples from the borehole drilled with a depth of 0.38 m at the Ugii Nuur Lake bottom. The analysis of the radio-carbon test, which is used for determination of sediment age, shows that the age of the Ugii Nuur Lake would be 2880 ± 50 years at a depth of 1.6–2.0 m [17].

## 2. Materials and Methods

#### 2.1. Study Area

^{2}, 38.2% of which belongs to the Arkhangai province of Central Mongolia. The lake exists in the Arkhangai province, which is about 350 km to the west of the capital city Ulaanbaatar (Figure 2) [10,12,16]. The lake has fresh water with mineralization of 0.499 g∙l

^{−1}, which is one of the biggest steppe lakes in Mongolia. The main surface inflow is the Khogshin Orkhon river, which is one of the tributaries of the Orkhon river. The lake has a width of 7.9 km from west to east and 5.3 km from north to south, and the shoreline length is 24.7 km. The surface area of the lake varies between 25.3 to 25.7 km

^{2}with a mean depth of 6.6 m, and the corresponding mean volume is 0.17 km

^{3}[11]. The maximum depth of the lake is observed in the center of the lake, with a value of 15.3 m. The basin area of the lake is 5020 km

^{2}[11].

#### 2.2. Data Sources

#### 2.3. Methods

#### 2.3.1. Lake Surface Area Calculation

#### 2.3.2. Mann-Kendall (MK) Analytical Method

_{0}and, if ${\mathrm{UF}}_{\mathrm{k}}$ > t

_{0}, this indicates that there is an obvious change trend in the sequence. If the result is multiplied by −1, then we get the reverse sequence’s statistic${\mathrm{UF}}_{\mathrm{k}}$, where ${\mathrm{UB}}_{\mathrm{k}}$ = 0. If there is an intersection between the two curves, the intersection is the beginning of the mutation [34]. When the two curves${\mathrm{UF}}_{\mathrm{k}}$, and ${\mathrm{UF}}_{\mathrm{k}}$ intersect and the intersection point is between the confidence lines, then the intersection point is the abrupt point. According to the test, if between the confidence lines that were defined from the processing of the data the value “zero” is included, then these values present mean values that are statistically equal. Thus, confidence lines are significant levels [35].

#### 2.3.3. Innovative Trend Analysis Method (ITAM)

#### 2.3.4. Sen’s Slope Estimator Test

#### 2.3.5. Analysis and Estimation of Climate and Hydrological Variables Influencing the Water Surface Area of the Lake

^{−1}), ${\mathrm{e}}_{0}$ is the water vapor pressure computed by water surface temperature (hPa),and${\mathrm{e}}_{2}$ is the water vapor pressure at 2.0 m above the ground surface (hPa).

## 3. Results and Discussion

#### 3.1. Changes in Lake Water Surface Area

^{2}, while the smallest area was 21.80 km

^{2}in 2011. The average water surface area of the Ugii Nuur Lake is about 24.90 km

^{2}. In 1986, the lake area was 26.04 km

^{2}and then it decreased to 24.40 km

^{2}in 2018. Long-term observations of the water surface area of the lake revealed that the lake area has decreased by 13.5% within the last 33 years (Figure 5).

#### 3.2. Trend Analysis

#### 3.2.1. Air Temperature Analysis

#### 3.2.2. Precipitation Analysis

#### 3.2.3. River Discharge Analysis

#### 3.2.4. Evaporation Analysis

#### 3.2.5. Analysis of the Water Surface Area of the Lake

#### 3.3. Impact of Cimate Parameters and Water Balance Components on the Water Surface Area of the Ugii Nuur Lake

^{2}), $\mathrm{Q}$ is total annual river discharge (mm), and is total annual evaporation (mm).

^{2}= 0.64 and p < 0.0001, respectively. It means that 64% of the variations in the water surface area of the Ugii Nuur Lake related to the variability of the total annual evaporation and the total annual river discharge by the equation. The remaining 36% can be explained by other factors that were not chosen for the regression model. The surface area of the lake was found using Equation (17) and then compared with the values calculated from the satellite imagery (Figure 13).

## 4. Conclusions

## Author Contributions

## Funding

## Acknowledgments

## Conflicts of Interest

## References

- Dorjsuren, B.; Yan, D.; Wang, H.; Chonokhuu, S.; Enkhbold, A.; Davaasuren, D.; Girma, A.; Abiyu, A.; Jing, L.; Gedefaw, M. Observed trends of climate and land cover changes in Lake Baikal basin. Environ. Earth Sci.
**2018**, 77, 725. [Google Scholar] [CrossRef] - Lioubimtseva, E.; Cole, R.; Adams, J.M.; Kapustin, G. Impacts of climate and land-cover changes in arid lands of Central Asia. J. Arid Environ.
**2005**, 62, 285–308. [Google Scholar] [CrossRef] - Lioubimtseva, E.; Simon, B.; Faure, H.; Faure-Denard, L.; Adams, J.M. Impacts of climatic change on carbon storage in the Sahara–Gobi desert belt since the Last Glacial Maximum. Global Planetary Change
**1998**, 16–17, 95–105. [Google Scholar] [CrossRef] - Malsy, M.; Aus der Beek, T.; Eisner, S.; Flörke, M. Climate change impacts on Central Asian water resources. Adv. Geosci.
**2012**, 32, 77–83. [Google Scholar] [CrossRef] [Green Version] - Lioubimtseva, E.; Henebry, G.M. Climate and environmental change in arid Central Asia: Impacts, vulnerability, and adaptations. J. Arid Environ.
**2009**, 73, 963–977. [Google Scholar] [CrossRef] - Nandintsetseg, B.; Greene, J.S.; Goulden, C.E. Trends in extreme daily precipitation and temperature near lake Hövsgöl, Mongolia. Internat. J. Climatol.
**2007**, 27, 341–347. [Google Scholar] [CrossRef] - Liancourt, P.; Boldgiv, B.; Song, D.S.; Spence, L.A.; Helliker, B.R.; Petraitis, P.S.; Casper, B.B. Leaf-trait plasticity and species vulnerability to climate change in a Mongolian steppe. Glob. Change Biol.
**2015**, 21, 3489–3498. [Google Scholar] [CrossRef] - Tao, S.; Fang, J.; Zhao, X.; Zhao, S.; Shen, H.; Hu, H.; Tang, Z.; Wang, Z.; Guo, Q. Rapid loss of lakes on the Mongolian Plateau. Proc. Natl. Acad. Sci. USA
**2015**, 112, 2281–2286. [Google Scholar] [CrossRef] [Green Version] - Wang, W.; Ma, Y.; Feng, Z.; Narantsetseg, T.; Liu, K.-B.; Zhai, X. A prolonged dry mid-Holocene climate revealed by pollen and diatom records from Lake Ugii Nuur in central Mongolia. Quat. Int.
**2011**, 229, 74–83. [Google Scholar] [CrossRef] - Walther, M.; Gegeensuvd, T. Ugii Nuur (Central Mongolia) Paleo Environmental Studies of Lake Level Fluctuations and Holocene Climate Change. Geographica-Oekologica
**2005**, 2, 36. [Google Scholar] - Jimee, T. A catalog of lakes in Mongolia; Shuvuun Saaral Publishing: Ulaanbaatar, Mongolia, 2000; pp. 15–16. [Google Scholar]
- Schwanghart, W.; Schütt, B.; Walther, M. Holocene climate evolution of the Ugii Nuur basin, Mongolia. Adv. Atmos. Sci.
**2008**, 25, 986–998. [Google Scholar] [CrossRef] [Green Version] - Schwanghart, W.; Schütt, B. Holocene morphodynamics in the Ugii Nuur basin, Mongolia—insights from a sediment profile and 1D electrical resistivity tomography. Zeitschrift für Geomorphologie, Supplementary Issues
**2008**, 52, 35–55. [Google Scholar] [CrossRef] - Tsegmid, S. Physical geography of Mongolia; Institute of Geography and Permafrost, Mongolia, Mongolian Academy of Sciences, Press of State Publishing: Ulaanbaatar, Mongolia, 1969; pp. 148–153. [Google Scholar]
- Fukumoto, Y.; Kaoru, K.; Orkhonselenge, A.; Ganzorig, U. Holocene environmental changes in northern Mongolia inferred from diatom and pollen records of peat sediment. Quat. Int.
**2012**, 254, 83–91. [Google Scholar] [CrossRef] - Wang, W.; Ma, Y.; Feng, Z.; Meng, H.; Sang, Y.; Zhai, X. Vegetation and climate changes during the last 8660 cal. a BP in central Mongolia, based on a high-resolution pollen record from Lake Ugii Nuur. Chin. Sci. Bul.
**2009**, 54, 1579–1589. [Google Scholar] [CrossRef] [Green Version] - Pagma, K.; Peck, J.A.; Fowell, S.J. Lake Systems and Paleoclimate investigation of the Holocene, Mongolia. In Proceedings of the Mongolian Academy of Sciences; Mongolian Academy of Sciences: Ulaanbaatar, Mongolia, 2002; Volume 42, pp. 67–89. [Google Scholar]
- Information and Research Institute of Meteorology Hydrology and Environment of Mongolia. Assessment of Water Resources of Lakes in Mongolia Based on Land and Satellite Data Information; Project report. Press of Admon printing: Mongolia, Ulaanbaatar, 2018; pp. 123–124. [Google Scholar]
- Bai, J.; Chen, X.; Li, J.; Yang, L.; Fang, H. Changes in the area of inland lakes in arid regions of central Asia during the past 30 years. Environ. Monit. Assess.
**2011**, 178, 247–256. [Google Scholar] [CrossRef] - Huang, J.; Ji, M.; Xie, Y.; Wang, S.; He, Y.; Ran, J. Global semi-arid climate change over last 60 years. Clim. Dyn.
**2016**, 46, 1131–1150. [Google Scholar] [CrossRef] [Green Version] - Valeyev, A.; Karatayev, M.; Abitbayeva, A.; Uxukbayeva, S.; Bektursynova, A.; Sharapkhanova, Z. Monitoring Coastline Dynamics of Alakol Lake in Kazakhstan Using Remote Sensing Data. Geosciences
**2019**, 9, 404. [Google Scholar] [CrossRef] [Green Version] - Li, X.-Y.; Xu, H.-Y.; Sun, Y.-L.; Zhang, D.-S.; Yang, Z.-P. Lake-Level Change and Water Balance Analysis at Lake Qinghai, West China during Recent Decades. Water Resour. Manag.
**2007**, 21, 1505–1516. [Google Scholar] [CrossRef] - Yin, X.; Nicholson, S.E. The water balance of Lake Victoria. Hydrol. Sci. J.
**1998**, 43, 789–811. [Google Scholar] [CrossRef] - Tamaddun, K.A.; Kalra, A.; Bernardez, M.; Ahmad, S. Effects of ENSO on Temperature, Precipitation, and Potential Evapotranspiration of North India’s Monsoon: An Analysis of Trend and Entropy. Water
**2019**, 11, 189. [Google Scholar] [CrossRef] [Green Version] - Dorjsuren, B.; Yan, D.; Wang, H.; Chonokhuu, S.; Enkhbold, A.; Yiran, X.; Girma, A.; Gedefaw, M.; Abiyu, A. Observed Trends of Climate and River Discharge in Mongolia’s Selenga Sub-Basin of the Lake Baikal Basin. Water
**2018**, 10, 1436. [Google Scholar] [CrossRef] [Green Version] - Archive and Database center at the National Agency of Meteorology and Environment of Mongolia. Available online: http://namem.gov.mn/ (accessed on 15 September 2019).
- USGS Global Visualization Viewer. Available online: https://glovis.usgs.gov (accessed on 1 March 2013).
- McFeeters, S.K. The use of the Normalized Difference Water Index (NDWI) in the delineation of open water features. Int. J. Remote Sens.
**1996**, 17, 1425–1432. [Google Scholar] [CrossRef] - Ma, M.; Wang, X.; Veroustraete, F.; Dong, L. Change in area of Ebinur Lake during the 1998–2005 period. Int. J. Remote Sens.
**2007**, 28, 5523–5533. [Google Scholar] [CrossRef] - Lu, S.; Ouyang, N.; Wu, B.; Wei, Y.; Tesemma, Z. Lake water volume calculation with time series remote-sensing images. Int. J. Remote Sens.
**2013**, 34, 7962–7973. [Google Scholar] [CrossRef] - Mao, D.; Wang, Z.; Yang, H.; Li, H.; Thompson, J.R.; Li, L.; Song, K.; Chen, B.; Gao, H.; Wu, J. Impacts of Climate Change on Tibetan Lakes: Patterns and Processes. Remote Sens.
**2018**, 10, 358. [Google Scholar] [CrossRef] [Green Version] - Gedefaw, M.; Wang, H.; Yan, D.; Song, X.; Yan, D.; Dong, G.; Wang, J.; Girma, A.; Ali, B.; Batsuren, D.; et al. Trend Analysis of Climatic and Hydrological Variables in the Awash River Basin, Ethiopia. Water
**2018**, 10, 1554. [Google Scholar] [CrossRef] [Green Version] - Gedefaw, M.; Yan, D.; Wang, H.; Qin, T.; Wang, K. Analysis of the Recent Trends of Two Climate Parameters over Two Eco-Regions of Ethiopia. Water
**2019**, 11, 161. [Google Scholar] [CrossRef] [Green Version] - Li, Y.; Sheng, Z.; Jing, J. Feature analysis of stratospheric wind and temperature fields over the Antigua site by rocket data. Earth Planet. Phys.
**2019**, 3, 414–424. [Google Scholar] [CrossRef] - Livada, I.; Synnefa, A.; Haddad, S.; Paolini, R.; Garshasbi, S.; Ulpiani, G.; Fiorito, F.; Vassilakopoulou, K.; Osmond, P.; Santamouris, M. Time series analysis of ambient air-temperature during the period 1970–2016 over Sydney, Australia. Sci. Total Environ.
**2019**, 648, 1627–1638. [Google Scholar] [CrossRef] - Gedefaw, M.; Yan, D.; Wang, H.; Qin, T.; Girma, A.; Abiyu, A.; Batsuren, D. Innovative Trend Analysis of Annual and Seasonal Rainfall Variability in Amhara Regional State, Ethiopia. Atmosphere
**2018**, 9, 326. [Google Scholar] [CrossRef] [Green Version] - Cherinet, A.A.; Yan, D.; Wang, H.; Song, X.; Qin, T.; Kassa, M.T.; Girma, A.; Dorjsuren, B.; Gedefaw, M.; Wang, H.; et al. Impacts of Recent Climate Trends and Human Activity on the Land Cover Change of the Abbay River Basin in Ethiopia. Adv. Meteorol.
**2019**, 2019, 14. [Google Scholar] [CrossRef] - Zhao, L.; Xia, J.; Xu, C.-y.; Wang, Z.; Sobkowiak, L.; Long, C. Evapotranspiration estimation methods in hydrological models. J. Geogr. Sci.
**2013**, 23, 359–369. [Google Scholar] [CrossRef] - Mbanguka, R.P.; Lyon, S.W.; Holmgren, K.; Girons Lopez, M.; Jarsjö, J. Water Balance and Level Change of Lake Babati, Tanzania: Sensitivity to Hydroclimatic Forcings. Water
**2016**, 8, 572. [Google Scholar] [CrossRef] [Green Version] - Dalton, J. Experimental Essays on the Constitution of Mixed Gases: On the Force of Steam or Vapour from Water or Other Liquids in Different Temperatures, Both in a Torricelli Vacuum and in Air; on Evaporation; and on Expansion of Gases by Heat. Mem. Liter. Philosoph. Soc. Manch.
**1802**, 5, 536–602. [Google Scholar] - Penman, H.L.; Keen, B.A. Natural evaporation from open water, bare soil and grass. Proc. R. Soc. Lond. Series, A. Mathemat. Physic. Sci.
**1948**, 193, 120–145. [Google Scholar] [CrossRef] [Green Version] - Xu, C.Y.; Singh, V.P. Cross Comparison of Empirical Equations for Calculating Potential Evapotranspiration with Data from Switzerland. Water Resour. Manag.
**2002**, 16, 197–219. [Google Scholar] [CrossRef] - Gombo, D. Surface Water Regime and Resources in Mongolia; Admon Printing: Ulaanbaatar, Mongolia, 2015; pp. 120–156. [Google Scholar]
- Magnus, G. Versuche über die Spannkräfte des Wasserdampfs. Ann. Phys.
**1844**, 137, 225–247. [Google Scholar] [CrossRef] [Green Version] - Matveev, L.T. Fundamentals of General Meteorology: Physics of the Atmosphere; Hydrometeorological press: Leningrad, Russia, 1967. [Google Scholar]
- Fifth generation ECMWF atmospheric ReanAlysis of the global climate (ERA5). Available online: https://cds.climate.copernicus.eu/ (accessed on 14 June 2018).
- WMO. Guide to Meteorological Instruments and Methods of Observation WMO-No. 8; WMO: Geneva, Switzerland, 2008. [Google Scholar]
- Hellman, G. Über die Bewegung der Luft in den untersten Schichten der Atmosphäre. Meteorol Z.
**1916**, 34, 273–285. [Google Scholar] - Tar, K.; Lázár, I.; Gyarmati, R. Statistical Estimation of the Next Day’s Average Wind Speed and Wind Power. In Proceedings of the Perspectives of Renewable Energy in the Danube Region, Budapest, Hungary, 26–27 March 2015; pp. 175–191. [Google Scholar]
- Sawaya, K.E.; Olmanson, L.G.; Heinert, N.J.; Brezonik, P.L.; Bauer, M.E. Extending satellite remote sensing to local scales: Land and water resource monitoring using high-resolution imagery. Remote Sens. Environ.
**2003**, 88, 144–156. [Google Scholar] [CrossRef] - Shang, S.; Shang, S. Simplified Lake Surface Area Method for the Minimum Ecological Water Level of Lakes and Wetlands. Water
**2018**, 10, 1056. [Google Scholar] [CrossRef] [Green Version] - Fang, J.; Li, G.; Rubinato, M.; Ma, G.; Zhou, J.; Jia, G.; Yu, X.; Wang, H. Analysis of Long-Term Water Level Variations in Qinghai Lake in China. Water
**2019**, 11, 2136. [Google Scholar] [CrossRef] [Green Version] - Chebud, Y.A.; Melesse, A.M. Modelling lake stage and water balance of Lake Tana, Ethiopia. Hydrol. Process.
**2009**, 23, 3534–3544. [Google Scholar] [CrossRef] - Du, Y.; Berndtsson, R.; An, D.; Zhang, L.; Hao, Z.; Yuan, F. Hydrologic Response of Climate Change in the Source Region of the Yangtze River, Based on Water Balance Analysis. Water
**2017**, 9, 115. [Google Scholar] [CrossRef] [Green Version] - Liao, J.; Shen, G.; Li, Y. Lake variations in response to climate change in the Tibetan Plateau in the past 40 years. Int. J. Digit. Earth
**2013**, 6, 534–549. [Google Scholar] [CrossRef] - Orkhonselenge, A.; Komatsu, G.; Uuganzaya, M. Middle to late Holocene sedimentation dynamics and paleoclimatic conditions in the Lake Ulaan basin, southern Mongolia. Géomorphol. Relief Process. Environ.
**2018**, 24, 351–363. [Google Scholar] [CrossRef] - Krapivin, V.F.; Mkrtchyan, F.A.; Rochon, G.L. Hydrological Model for Sustainable Development in the Aral Sea Region. Hydrology
**2019**, 6, 91. [Google Scholar] [CrossRef] [Green Version] - Chikita, K.A.; Oyagi, H.; Aiyama, T.; Okada, M.; Sakamoto, H.; Itaya, T. Thermal Regime of A Deep Temperate Lake and Its Response to Climate Change: Lake Kuttara, Japan. Hydrology
**2018**, 5, 17. [Google Scholar] [CrossRef] [Green Version] - Goshime, D.W.; Absi, R.; Ledésert, B. Evaluation and Bias Correction of CHIRP Rainfall Estimate for Rainfall-Runoff Simulation over Lake Ziway Watershed, Ethiopia. Hydrology
**2019**, 6, 68. [Google Scholar] [CrossRef] [Green Version] - Tao, S.; Fang, J.; Ma, S.; Cai, Q.; Xiong, X.; Tian, D.; Zhao, X.; Fang, L.; Zhang, H.; Zhu, J.; et al. Changes in China’s lakes: Climate and human impacts. Nat. Sci. Rev.
**2019**, 7, 132–140. [Google Scholar]

**Figure 1.**The Ugii Nuur Lake, northwest-facing view of the landscape in 2018. Photo by Uuganbat Tumur.

**Figure 6.**Linear regression for a relationship between water level and surface area of the Ugii Nuur Lake.

**Figure 7.**The trend of annual average air temperature at the Ugii Nuur Lake site (where UF and UB are parameters of the change, UB = −UF).

**Figure 8.**The trend of total annual precipitation at the Ugii Nuur Lake site (where UF and UB are parameters of the change, UB = −UF).

**Figure 9.**The trend of the total annual discharge of the Khogshin Orkhon River, which is an inflow of the Ugii Nuur Lake (where UF and UB are parameters of the change, UB = −UF).

**Figure 10.**The trend of total annual evaporation at the Ugii Nuur Lake (where UF and UB are parameters of the change, UB = −UF).

**Figure 11.**The trend of the annual mean lake area of the Ugii Nuur Lake (where UF and UB are parameters of the change, UB = −UF).

**Figure 12.**Linear regression for a relationship between the water surface area of the lake and variables such as (

**a**) air temperature, (

**b**) precipitation, (

**c**) river flow, and (

**d**) evaporation.

**Figure 13.**A relationship between lake surface areas estimated from satellite and multiple regression equation.

Years | 1986 | 1987 | 1988 | 1989 | 1990 | 1991 | 1992 | 1993 | 1994 | 1995 | 1996 |

Lake area | 26.04 | 25.96 | 25.84 | 24.45 | 25.98 | 26.74 | 25.74 | 26.43 | 26.48 | 26.78 | 25.88 |

Years | 1997 | 1998 | 1999 | 2000 | 2001 | 2002 | 2003 | 2004 | 2005 | 2006 | 2007 |

Lake area | 25.91 | 26.17 | 25.89 | 27.11 | 25.69 | 24.81 | 24.95 | 25.30 | 25.43 | 24.80 | 24.35 |

Years | 2008 | 2009 | 2010 | 2011 | 2012 | 2013 | 2014 | 2015 | 2016 | 2017 | 2018 |

Lake area | 23.68 | 22.79 | 22.24 | 21.80 | 22.16 | 22.52 | 23.37 | 23.13 | 24.19 | 24.38 | 24.60 |

**Table 2.**Comparison of results by Mann-Kendal (MK), Innovative Trend (ITAM), and Sen’s Slope Estimator Test.

No | Parameters | Mann-Kendall Trend Analysis | Innovative Trend Analysis | Sen’s SlopeEstimator Test Approach |
---|---|---|---|---|

1 | Trend of annual average air temperature | 4.595 *** | 16.076 *** | 0.065 |

2 | Trend of total annual precipitation | −0.902 | −0.542 | −0.888 |

3 | Trend of total annual river discharge | −5.392 *** | −6.511 *** | −0.015 |

4 | Trend of total annual evaporation | 4.385 *** | 4.328 *** | 2.256 ** |

5 | Trend of water surface area | −6.021 *** | −0.896 | −0.102 |

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

## Share and Cite

**MDPI and ACS Style**

Sumiya, E.; Dorjsuren, B.; Yan, D.; Dorligjav, S.; Wang, H.; Enkhbold, A.; Weng, B.; Qin, T.; Wang, K.; Gerelmaa, T.;
et al. Changes in Water Surface Area of the Lake in the Steppe Region of Mongolia: A Case Study of Ugii Nuur Lake, Central Mongolia. *Water* **2020**, *12*, 1470.
https://doi.org/10.3390/w12051470

**AMA Style**

Sumiya E, Dorjsuren B, Yan D, Dorligjav S, Wang H, Enkhbold A, Weng B, Qin T, Wang K, Gerelmaa T,
et al. Changes in Water Surface Area of the Lake in the Steppe Region of Mongolia: A Case Study of Ugii Nuur Lake, Central Mongolia. *Water*. 2020; 12(5):1470.
https://doi.org/10.3390/w12051470

**Chicago/Turabian Style**

Sumiya, Erdenesukh, Batsuren Dorjsuren, Denghua Yan, Sandelger Dorligjav, Hao Wang, Altanbold Enkhbold, Baisha Weng, Tianlin Qin, Kun Wang, Tuvshin Gerelmaa,
and et al. 2020. "Changes in Water Surface Area of the Lake in the Steppe Region of Mongolia: A Case Study of Ugii Nuur Lake, Central Mongolia" *Water* 12, no. 5: 1470.
https://doi.org/10.3390/w12051470