Sunday, Dec 12, 2021 09:00 [IST]
Last Update: Sunday, Dec 12, 2021 03:31 [IST]
The Mountain Institute India (TMI) jointly with Khani-khola and Bagey Khola Watershed Committee is currently implementing a project “Spring Rejuvenation and springshed-based Watershed Development” funded by the National Mission on Himalayan Studies (Ministry of Environment and Forests & CC, Government of India) through nodal agency GB Pant National Institute of Himalayan Environment (GBPNIHE); and by the National Bank for Agriculture and Rural Development (NABARD), Gangtok Regional Office, Sikkim. Springshed-based watershed development involves treatment of the entire catchment areas based on geohydrology study to ensure conservation and regeneration of all its natural resources, especially springs. Spring revival through recharge area treatment measures, lake revival through monsoon water harvesting, agroforestry development, livelihood enhancement through village water security measures, and water storage infrastructure are salient features of the project.
The mountains of Sikkim are primarily dependent on rainwater for recharging their aquifers. The glacier-fed rivers flow through the valley of the hills and mountains and thus water is not available for both plants and animals. Mountains absorb a high amount of rainwater and are the “water towers” supplying fresh water to the lowlands. Unfortunately, springs, lakes and rivers are drying up, wetlands are shrinking, and water flow is becoming increasingly unpredictable in the Himalayas.
A seasonal spring at Central Pendam GPU
The Rural Development Department (RDD) Government of Sikkim launched a scientific initiative namely “spring-shed development“ (Dhara Vikas) in the year 2008 in active collaboration with WWF-India, People’s Science Institute, Dehradun, ACWADAM, Pune, and TMI India in the highest and the steepest landscapes facing scarcity of water, by using rainwater harvesting, geo-hydrology, and GIS techniques. Principles of geohydrology, watershed, and GIS were integrated to conceptualize this new initiative which was launched to revive, restore and rehabilitate dying springs and lakes in drought-prone areas in view of the increasing threat from environmental changes resulting from changes in climate, land use (rapid development of hydropower, pharmaceutical companies, factories/ industries, and road building), and demography. It is widely accepted that springs in the mountainous region are drying. While there is a lack of complete data set to validate this information. During 2008-2012 The RDD and TMI India jointly developed a spring atlas covering around 700 springs mostly from South and West Sikkim. The development of database since then is yet to be updated to complete.
Dr. Ghanashyam Sharma, Head of TMI during early 2018 conceptualized a study to prepare a comprehensive Geohydrology report and a Village Water Security Plan (VWSP) at the GPU level. The main objectives of the study were to identify the current issues related to drinking water, dependency for drinking water to local springs, assess the gravity-based water supply systems, and assess current water requirements and the state of water governance in the Khani-khola and Bagey-khola watersheds. The VWSP is a comprehensive prior need-assessment report/strategy developed for the implementation of future water supply schemes including the gravity-based water supply schemes, water management, rooftop water harvesting structures, and so on.
The degradation of the catchment areas followed by new challenges brought by climate change and a host of other land-use changes owing to developmental activities (hydropower tunnelling, road building, establishments of Pharmaceuticals and other cemented structures in the mountains and hill slopes, urbanization etc.) have decreased the mean discharge of springs and many disappeared already. This problem is more acute in the dry and rain shadow areas of Sikkim. In the last decade, this complexity of water scarcity and management has been increasingly observed, bringing the state government and organizations to mobilize their resources in convergence with national policies and programs to manage them.
Bagey-Khola and Khani-khola Watershed in Pendam under Duga Block, East Sikkim
Ground-water resources form the backbone of the water supply in the rural areas of Sikkim. ‘Springs, seepages, rivulets such as khola, simsaar-kholyang, kholsa, jhora, kuwa, pandhera, pokhari, and dhara’ form the main source of water supply to rural and urban habitations in the Sikkim Himalayan region. Nearly one million people reside in Sikkim. The entire population in the Sikkim Himalayan region depends on natural water sources for fulfilling their domestic and livelihood needs such as drinking water, dairy, sanitation, and irrigation. This dependence implies that with changing climatic conditions and rainfall patterns, around 60% of villages of East, South, and West Sikkim face water scarcity. As high as 20 – 30% of the perennial natural water sources have already dried up and 20% –30% of perennial springs turned seasonal.
Springs ecosystems are geographically abundant, geomorphologically diverse, and bio-culturally productive, but are highly jeopardized by anthropogenic activities. More than a century of scientific discussion about the wide array of ecohydrological factors influencing springs has been informative but has yielded little agreement on their classification. Therefore, we applied EbA as a strategy for the integrated management of land, water sources and their catchments, forests, and living resources that promote conservation and sustainable use in an equitable way.
We established different “green water infrastructures” such as rainwater diversion channels, gabion walls, retention ponds, recharge ponds, staggered infiltration trenches, reconstruction, and revival of dried lakes to increase water yield from the ecosystem. Furthermore, our team attempted to understand the effect of rainfall, physiography, lithology, slope and slope aspect, land use, vegetation, altitude, soil type, and anthropogenic interferences (e.g. road construction, deforestation, settlement, etc), to analyze recharge of the springs and dried lakes in the Khani-khola and Bagey-khola watersheds. This helped us to develop feasible options for rational use of the water available and EbA options for sustainable water conservation and supply. It is expected that the results of this study would be useful to address the prevailing water supply problem in these watersheds.
Lakes had played an important role in naturally recharging groundwater in Khani-khola and Bagey-khola watersheds. Around 30 years ago, these lakes had adequate groundwater recharge capacity, to even supplement the lean period discharge of springs and streams located downstream. Reviving dried-up lakes by improving their catchment, de-silting to enhance their water holding capacity, and storing water from a perennial source or by arresting the rainwater in the monsoon was a prerequisite for the revival of Shepatar and Aaley-gairi lakes. Springs and lakes have reduced discharge over the years and at many places, the infiltration catchments have been degraded. Therefore, drinking water spells the most significant challenge for the Central and West Pendam GPUs. Lakes, traditionally have played an important role in groundwater recharge, are seen as critical to ensuring the sustainability of the ecosystem in these watersheds and their revival was therefore imperative. Our objective was to improve sub-surface reservoirs which are technically feasible alternatives for accumulating surplus monsoon runoff and store a substantial quantity of water. These sub-surface reservoirs, located in suitable hydrogeological situations, are environment-friendly and economically viable propositions for recharging the aquifers.
Aaley-gairi lake is situated under Budang-Karemey GPU, between 27o 13’ 4.629” N and 88o 32’ 28.427” E (Accuracy (4.6 m) at an altitude of 1820 m in the East district of Sikkim, India. The length of the Aaley-gairi lake is 47.27 m (128’) long with a width of 17.27 m (57’). The depth of the lake is 2.54 m (8.25’). As per the calculation following Taube (2000), the water collected in the lake during the end of July 2021 was around 816.35 m3 (i.e., 8,16, 352.9 Ltrs) which is up to the marked excavated depth that is 1 m. The full capacity of the lake when fully filled up is 2073.54 m3 (i.e., 20,73, 536 Ltrs).
Sherpatar Pokhari is situated between 27o 13’ 12.81” N and 88o 31’ 15.030” E at an altitude of 1721 m almost at the top of the hill of West Pendam GPU. This area was initially inhabited by the indigenous Sherpa tribe of Sikkim. There was a lake around 60 years ago which later dried up due to unknown reasons. Cattle grazing was prevalent in the forests surrounding the lake in the past 30 years which was later discontinued. The total length of the lake is 44.24 m long and 15.75 m in width with a depth of 4.39 m. During monsoon 2021 (June to September), the total amount of rain-water collected in the lake was between 101,000 to 1,130,800 Ltrs depending upon the rainfall intensity. Of the 120 days in four months, the Sherpatar area, which is located at the top of the mountainous forested area received approximately 1973 mm of rain in about 89 days. The infiltration rate was too high (>50 mm ha-1) due to coarse granular rock material and permeable rock fractures at the base of the lake.
Sherpatar and Aaley-gairi lakes and their surrounding forests including the Gadi Sacred Forest was identified by geohydrology study conducted by TMI India and isotope study conducted by Mr. Deepak Dhakal Sikkim University as the catchments of 38 perennial springs. This information was authenticated with the citizen science by consulting the community experts on the water who have experienced changes in spring discharge, discharge rates of rivers and rivulets, and the seasonal springs. There are around 3204 households (16188 persons) dependent on these springs for drinking water and for other domestic chores which are both original inhabitants and outsiders residing as labour or working in the companies/government offices.
The drinking water supply in Khani-khola and Bagey-khola watersheds is completely dependent on the availability of water in the springs. As of date, water availability of the springs have been comparatively high as compared to yesteryears, as it used to sharply decline by October onwards. This is attributed to the aquifer restoration and catchment improvements through the project. Water availability is high during monsoon while during dry months spring discharge remains utterly minimum. While this year, the discharge rates and duration of discharge have increased considerably. In the villages reeling under water scarcity, the project has constructed storage tanks to store water for equitable distribution. These tanks are built to store free-flowing water from springs and to meet the water demand in villages where perennial spring discharge is low and insufficient to meet the demand.
TMI acknowledges the support provided by NABARD. This project could not have been successful without technical support of RDD, members of Budang-Kamerey GPU, Central and West Pendam GOPU, and the active participation provided by Khani-khola and Bagey-khola Watershed Committees.