Ladakh is a cold desert and during winter agriculture is not practiced due frozen ground and low air temperature. During spring season, water requirement for sowing increases whereas streams dry up. With annual rainfall of less than 50 millimetres (2.0 in), agriculture in Ladakh is solely dependent on snow and glacier meltwater. Due to climate change, the region experiences hotter summers with increase in melts along with shift in the timing and precipitation of the melts.
Ice Stupa is a form of glacier grafting technique that creates artificial glaciers, used for storing winter water , which otherwise goes waste in form of conical shaped ice heap. During summer, when water is scarce, the Ice Stupa melts to increase water supply for crops. Ice Stupa was innovated by Sonam Wangchuk in Ladakh, India and the project is undertaken by the NGO Students’ Educational and Cultural Movement of Ladakh.
since these are based on horizontal ice formation, they need very high altitude locations (above 4,000m), constant maintenance and a north-facing valley to shade the ice from the spring sun. This is achieved by freezing the stream water vertically in the form of huge ice towers or cones of 30 to 50m height that look very similar to the local sacred mud structures called Stupa or Chorten. These ice mountains can be built right next to the village itself where the water is needed. Very little effort or investment would be needed except for laying one underground pipeline from a higher point on the stream to the outskirts of the village. Normally the head difference is easily 100m over a distance of roughly one to three kilometers.
The idea is very simple and needs no pumps or power. We all know that water maintains its level. Therefore water piped from 60m upstream would easily rise close to 60m up from ground when it reaches the village. For simplicity we can imagine that the pipe is mounted on a mobile-phone tower of that height, and then it is made to fall from that height in cold Ladakhi winter nights when it is -30 to -50°C outside (with wind chill factor). The water would freeze by the time it reaches the ground and slowly form a huge cone or Ice Stupa roughly 30 to 50m high. In reality we won’t even need a tower structure since we can let the piped water first freeze at the ground level and then mount higher meter by meter as the thickness of the ice grows, finally reaching close to the height of the source.
The idea is also to conserve this tower of ice as long into the summer as possible so that as it melts, it feeds the fields until the real glacial melt waters start flowing in June. Since these ice cones extend vertically upwards towards the sun, they receive fewer of the sun’s rays per the volume of water stored; hence, they will take much longer to melt compared to an artificial glacier of the same volume formed horizontally on a flat surface.
Engineering notes
Melting is nothing but individual molecules either remain attached to the ice matrix, or release and become part of the liquid mass around it. In fact this happens even if both the ice and liquid are exactly at freezing temperature , it’s just that if no more ice is melting, the molecules move off the ice and back onto the ice at the same rate, so we feel nothing is happening.
So the when the ice is still melting, the number of molecules falling off the solid and into the liquid is greater than the number reattaching. If it’s freezing, the molecules are attaching more than falling. As you can imagine, only molecules at the surface can do this, and the process takes time as well as needing heat input, from environment, and as always, increasing the entropy of the system.Because only molecules at the surface have the option to fall off, surface to volume ratio is quite important. This ratio is directly proportional to surface area.
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