Mountainous water of Sikkim and its conservation

by DK PRADHAN
source: SikkimNow

Essaying the magnificent role of water harvesting, a hill is a complex phenomenon; in other words, the hill itself is a paradigm of rain water harvesting. The roles of soil water, vadose water and saturated zone are incomparable and if any of these are de-linked, the water reservoir of a hill may pass to another water saturated zone. The pores of hill soil matrix, in soil column, typically act as capillary tubes in capillary fringes of soil, while, the capillary actions of the capillary fringes, above the saturated zone, act as the instruments to collect the water. Such action of soil pores immediately above the water table tenaciously retains water for the underlying water table. Soil water is a prerequisite for sustainable development of forest areas. In addition, the water retaining trees along the ridge to the base offer a good prototype for watershed development according to the altitudinal suitability of species for rendering water and water conservation for larger stakes. The soil moisture requirement varies from plant to plant. Moisture loving plants are available in the sliding and sinking zones and the growth of Alnus nepalensis [Utis] in sliding zones is a natural bioengineering evolution of forests.
At the advent, the hills with bases facing streams are generally sources of hill water. This, because hills without proper water management are vulnerable to landslides and prone to natural calamities. In this respect, the vulnerability mapping of hills is an urgent need of the hour in the state of Sikkim as part of a long-term strategy. Abundance of Alnus (utis), Macaranga (malata), Erythrina (phaledo), Viburnum (Asarey), Datura (datura) etc are signs of a healthy forest. Integrated growth of several regional or altitudinal species ensures sustainable development of the soil matrix, and in terms of biodiversity, such a paradigm is an exemplary form of another microclimatic zone or watershed. Generally, the landslide prone areas are devastated regions and require moisture loving and moisture retaining plants matching the soil moisture and dry conditions respectively.
In the plains, digging a few feet can reach the water table which is not possible in the hills. The hills provide beautiful examples of natural geo-bio engineering for water harvesting. The hilltop is a container-like entity and generally in Sikkim, the slopes at the higher altitudes have alpine trees such as Dhupi, Pines, Abies, Taxus etc. In the middle order, the forest of Machilus , Machelia , Spondias, and others are available. Likewise, at the base, forests of Schima wallichi, Castanopsis, Cedrela etc are seen. The general outlook on dhupi and other pines mistakenly believes that these plants absorb water and desert soil. It is however felt that the plantation of such trees at inappropriate areas is a major drawback although to a certain extent, the fast growth of pine and other dhupis in the higher altitudes leads to early drying of the soil and maintains ecological balance, preventing landslides.
Soil water, vadose water, capillary fringes and saturated zone play different roles in the natural water harvesting mechanism.
The rain water or water from other sources infiltrates the soil water and reaches vadose soil (at the rock or porous soil below soil water) at the sediments or rocky areas. The capillary action of capillary fringes, the layer above water table, trenches water and drains it out through cliffs. Mismanaged plans and wrong implementation of ridges to base treatment in three tiers approaches of top, middle and base, can result in devastation at the end. Such a devastated area cannot be retrenched in a day or a year, but requires decades or a century to rebuild.
Areas perennially under snow cover have very few vegetation of herbaceous nature. High soil moisture content and humic nature of alpine make a very fragile environment at the top. Generally, these hills or mountainous regions receive large amounts of rainfall as well. Likewise, such snowy mountainous belts are vulnerable to avalanches and landslides.
Nevertheless, just below the alpine forest, trees and shrubs are available even if only of moderate size. These forests are engaged in maintaining major ecological water harvesting role too. Destruction of such vegetation may result in lesser transpiration of soil moisture and ultimately affect soil fertility. Any disturbance in the natural equilibrium of an ecosystem, without regional forest planning, is ill advised.
Other forest types such as temperate, sub-temperate, sub-tropical and tropical forests are also found in the Sikkim hills and are responsible for the transpiration of soil water and provide water for the forest sustainability. These forests control the soil water runoff and soil erosion. The biodynamics of these forest types are in accord to the type of hills and microclimatic zones. Change of vegetation matrix and adaptation of new exotic species and removal of the natural habitat are the imposed threats to the Sikkim ecosystem.
According to the nature and properties of plants, water consumption levels differ, and eventually so do soil fertility and soil maintenance. Some of the identified water retaining plants of Sikkim recorded from reconnaissance of habitats and their fringes are Arundinaria racemosa (Sanu maling), Bambusa tulda (Mal bans), Bambusa vulgaris (Telai bans), Bambusa vulgaris var waminii (Lota bans), Dendrocalamus hamiltonii (Choya bans), Dendrocalamus himiltonii var edulis (Guliyo tama), Dendrocalamus patellaris (Neba), Dendrocalamus hookeri (Tili bans), Dendrocalamus sikkimensis (Bhalu bans), Dendrocalamus strictus (Bhalu bans), Dendrocalamus asper (Kabas bans), Phyllostachys manii (Kata bans), Phyllostachys nigra (Kalo ningalo), Schizostachyum capitatum (Gopa bans), Schizostachyum dullooa (Tokre bans), Schizostachyum latifolium (Dullo bans), Sinarundinaria hookerina (Parang), Sinarundinaria intermedia (Tite nigalo), Sinarundinaria maling (Maling), Sinarundinaria microphylla (Deo nigalo), Thamnocalamus aristatus (Rato nigalo) etc for Bamboos species, likewise, trees species are Ficus auriculata (Bhutuk), Ficus benghalensis (Bar), Ficus benjamina (Swami), Ficus glaberrima (Pakhuri), Ficus hederacea (Dudhe lahara), Ficus hirta (Khasreto), Ficus hispida (Kharsu/ kothedumar), Ficus lacor (Pakadi), Ficus nerrifolia (Dudhe), Ficus oligodon (Nimaro), Ficus palmate (Bedu), Ficus microcarpa (Sami), Ficus racemosa (Gular/ Dumri), Prunus napaulensis (Arupatey), Jambosa kurzii (Ambakey), Bischofia javanica (Kaijal), Albizzia marginata (Siris) Musa sikkimensis (Ban banara), Litsea polyantha (Ketmero), Elaeocarpus sikkimensis (Badrasey), Spondias axillaries (Lapshee), Bassia butyracea (Cheurey), Machilus edulis (Pomche), Juglans regia (Okar), Cedrela toona (Tuni), Cordia oblique (Bori) , Terminalia myriocarpa (Pani sanj), Schima wallichii (Chilauney), Castanopsis hystrix (Katus), Symplocos theifolia (Karaney), Abies webbiana (gobrey salla), Larix griffithi ( bargay salla), Michelia champaca (Champ), Castanopsis tribuloides (Patley katus) etc.
Traditional knowledge, refined from age old phenomenon and passed down from generation to generation and sanctified as is evident from the sacred space occupied by trees of the region are reflected in the plant species I have researched for water resource conservation. The testimonies of the elders and extant belief systems make people aware about conservation and its necessity. Dignified social planning is now necessary for the protection and preservation of water sources and their conservation.
Generally, lack of awareness proves costly matter when it comes to water conservation. The trees, geo-resources and animal habitat of invertebrates and vertebrates are important components of water conservation. Capillary fringes above the water table are the habitat of reptiles, birds, crabs, wild rat etc. They clear soil layer at the inner levels for their settlement at the capillary fringes of soil. Missing any of these bio and geo resources may damage the water source. In addition, a sustainable water source can be developed through integrated approaches of biotic and abiotic factors in accord to microclimatic zone at the capillary fringes.
Soil health is an important issue for vegetative growth, for the animals and for the abiotic factors. Lack of fertility, acidity and other relative factors destroy vegetation. In the midst of such nature, the movement of animals from one water source region to another may result in slow drying of water sources. The panorama of decades old vegetation cannot be rebuilt in a day or year. Eventually, as rain water runoff increases, it triggers further deterioration and leads to disaster. Therefore, the primary role of the soil health is significant for the management and maintenance of hills.
Shifting of water source locations from one point to another is an unusual and unwanted happening of hills. Deforestation at hilltops, increment of soil water run off, inability of rain water harvesting natural mechanism, changes in vegetation matrix, changes in animal matrix and other relative factors are the major reasons for such happenings. Drying of a water source is not a result of a day’s damage, but the outcome of continued recklessness which diverts the water capillary action of capillary fringes to other directions.
Construction of artificial tanks at a water sprout should be avoided. It should be instead located at the basal region as a harvesting site or tank without much damage to the ground condition.
Pure water, air and natural resources are the economy and capital of the hills. General awareness on the natural water harvesting mechanism of hills is necessary for the strategic protection and preservation of water sources. In connection to this, necessary vegetation of water retaining plants at lower and upper area of capillary fringes in hill, are mandatory for the perennial water source.
The State Government’s endeavor towards water conservation and implementation of water conservation plans is noteworthy and unparalleled. Close people’s participation, vulnerability mapping and sustainable strategy for the water conservation are the urgent requirements for the protection of water sources of Sikkim. Integrated natural regeneration as per the microclimatic zone needs to be proposed by the Gram Sabhas or competent authority. The Sikkim Himalaya holds such a variety of altitudinal gradients that within a hillock itself one can find all types of forests. Hence, planning with the proper knowledge of watershed and geological data will bear fruit when it comes to water conservation for the benefit of the people at large. Unscrupulous decisions on the vegetation matrix preparation should be avoided. Opinions and advice of regional experts and natural regeneration methodology may be adopted for the better water conservation.
[the writer is Principal Scientist, High Altitude Research Centre, Forests, Environment and Wildlife Management Department, Government of Sikkim]