A Time Series Change Analysis of Lake Area and Their Response to Climate Change: Case Study of Nainital Region Lakes, Kumaun Himalayan

Lake surface area change in Kumaun Himalayan lakes is a very important factor as it is directly related to the rainfall pattern of the area and followed by water management in the Kumaun lesser Himalayan region. Study of physiographic changes lakes in the Himalayan region is extremely important as these are the main source of fresh water and are strongly related to geodynamics, anthropogenic activities and regional climate changes. Somehow the lacustrine water is always affected by the lithology, topography, and anthropogenic activities around the lake system. The geometry of the lake is also controlled by lithology, physiography, and anthropogenic activities. The main challenge is to assess the stability of lakes and understand the effect of ongoing deformation, climate change impact and issues related to their augmentation as lowering of lakes may be attributed to excessive withdrawal and lack of recharge. As the low altitude is the zones under human reaches, the lakes of low altitude are under human interference and widely affected by anthropogenic activities. Water is a basic requisite for living beings such as humans and wildlife, food production, alleviation of poverty, food security, sustainable development etc. Population increment, drinking water consumption, reduced rainfall, water pollution, poor sanitation, decrease rainfall, groundwater levels and water scarcity are factors that drag India into a major threat. In Kumaun lesser Himalayan region, „water problem‟ is mainly due to poor management, ignorance, use of inappropriate technology in water management. Human interface with environ in Nainital area is started after 1841 as human habitation started after 1941 (Peeyush, 2013). After human habitation Nainital is continuously facing mass movement till now. Climate change has become an important factor (Huang, 2011 and Lie et al., 2013) to control the lake surface area and its volume as lake surface area change with respect to rainfall, glaciations, evaporation etc. long term monitoring and mapping of Kumaun Himalayan lakes can provide a better understanding of climate change and ultimately the understanding of management of water resources. The dynamics of lake surface area change can be indicator of local ecosystem change (Haifeng et al., 2017 and Ma, 2010). Landsat time series data is the medium resolution data which records earth‟s surface from 1972 to present (Roy, et al., 2014). The Landsat time series is open resource, having capacity to monitor temporal history. Many temporal studies have been done with the help of Landsat time series data to reveal spatial-temporal changes of high and mid altitude lakes of Himalayan region (Nie, 2013) (Liao, 2013). The main purpose of this study is to extract the surface area of lakes by maximum livelihood classification and manual method with the help of Landsat time series data from 1972 to present in order to make better understanding of climate change and its relation with lake surface area change. In this regard, it‟s an attempt to evaluate the past and present lake surface area change of Kumaun lesser Himalayan lakes.

Kumaun Himalayan lakes bounded between latitudes of 29º27‟30”-29º10‟30” N and longitudes of 79°50‟0”-79°28‟30”E. Kumaun Himalayan lakes are located in a densely populated valley of Kumaun Himalaya (Nainital district) of Uttarakhand. The study area experiences the climate of sub-tropical to sub-humid. The study area comes under the elevation range 474m to 2581m and slope range from 0° to 79.0672°. Lesser Himalayan region situated between main boundary thrust (MBT) in the southern regime and main central thrust (MCT) in the northern regime. Study area consist of eight natural lakes viz., Nainital, Bhimtal, Khurpatal, Naukuchiatal, Sattal, Pannatal, Harishtal, Lohakhamtal.

performed in all the satellite images later lake surface area has been extracted using supervised classification (maximum likelihood). (Need more detail description of the procedure) Further manual digitization of each lake has been performed to extract lake surface area of each lake of Kumaun lesser Himalaya. After extraction of lake surface area accuracy assessment has been performed. Flow chart of whole exercise is shown in Figure 2.

In the present study Landsat time series data is used which is medium resolution data. For extraction of lake surface area, Landsat 1 MSS collected on 01 December 1972 (one scene), of Landsat 3 TM and Landsat 5 TM collected on 15 October 1981 and 22 October 1992 (two scene), Landsat 7 ETM+ collected on 23 October 2002 (one scene), Landsat 8 OLI collected on 13 October 2013 (one scene) were used. The satellite images can be downloaded free from the USGS earth explorer.

ArcGIS geospatial package was used for the extraction of lake surface area. Digital elevation model (DEM) (AlosPal SAR) and topographic maps (Survey of India toposheet at 1:50000) used for preparation of other layer.

We attempt to extract surface area of Kumaun Lesser Himalayan lakes with the help of Landsat time series data. The graphical representation of present study results is shown in Figure 2. The from 1972 to 1981, a gradual decrement from 1982 to 2013 and slight increment from 2013 to 2017. Surface area of Nainital Lake in 1972 was 46.6642 hectare with time it became 56.3831, 55.4111, 48.4699, 47.2064, 48.4699 hectare in 1981, 1992, 2002, 2013 and 2017 respectively. Surface area of Khurpatal Lake was 4.32 hectare in 1972 with time the surface area of lakes changes 4.68, 4.3158, 4.0978, 3.82868 and 3.9978 hectare in 1981, 1992, 2002, 2013 and 2017 respectively. Surface area of Pannatal was 4.8516 hectare in 1972 with time the surface area of lakes changes 5.6764, 4.62923, 4.03339, 4.0416 and 4.03339 hectare in 1981, 1992, 2002, 2013 and 2017 respectively. Surface area of Sattal was 26.08534 hectare in 1972 with time the surface area of lakes changes 28.5478, 23.98863, 22.542, 21.53924 and 22.542 hectare in 1981, 1992, 2002, 2013 and 2017 respectively. Surface area of Bhimtal was 50.8565 hectare in 1972 with time the surface area of lakes changes 51.9624, 47.5912, 46.0353, 44.0296 and 45.0353 hectare in 1981, 1992, 2002, 2013 and 2017 respectively.

Surface area of Nakuchiatal was 32.3141 hectare in 1972 with time the surface area of lakes changes 34.2395, 25.4811, 24.9121, 24.9233 and 25.9121 hectare in 1981, 1992, 2002, 2013 and 2017 respectively. Surface area of Harishtal was 4.74188 hectare in 1972 with time the surface area of lakes changes 5.06, 4.512673, 3.13966, 3.09093 and 3.13766 hectare in 1981, 1992, 2002, 2013 and 2017 respectively. Surface area of Lohakhamtal was 3.24 hectare in 1972 with time the surface area of lakes changes 3.52987, 2.38658, 1.826, 1.81418 and 1.824 hectare in 1981, 1992, 2002, 2013 and 2017 respectively. Pictorial representation of lake surface area changes from 1972 to 2017 in Kumaun lesser Himalayan lakes is shown in Figure 4.

Global surface water explorer dataset has been used for data validation purpose, this dataset is a virtual time machine which provides high resolution maps with location and distribution of global surface water over the last 3 decades. This study describes temporal changes along the Kumaun Himalayan lakes from 1984 to 2017. In this dataset 3 million multi temporal orthorectified Landsat 5, 7, 8 satellite images have been used to quantify global surface water with special and temporal variability for the last 31 years from 1984 to 2017 at 30m resolution. Surface water dynamics and high resolution seasonality map have been recorded from coarse- special resolution satellite observation and Landsat satellite imagery at 5 year to 10 year intervals and ultimately leads to map seasonality and changes at continental sub-continental region. The Landsat data is classified as land, open water (fresh water and salty water) and non valid observations. The classification has been done by using 40,000 reference points, so very less probability of false water detection. The study found that lake of Kumaun Himalaya gradually shrinking.

The whole exercise concluded that of Kumaun Himalaya gradually shrinking. Shrinking lakes may results from many factors like high siltation, construction and encroachment in the catchment area, eutrophication of the lake water due to addition of solid waste, construction debris, comparative warming in Himalayan region and climate change, Over extraction and over dependent on lake water for drinking and irrigation purpose, sharp increase in human population, increase in anthropogenic pressure in the catchment area, Increase in tourist influx, Deforestation, lack of lake water management and long term planning.

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Department of Remote Sensing and GIS, Campus Almora, Soban Singh Jeena University, Almora, Uttarakhand, India-263601