Water has always been one of Kalimpong's most precious resources and has always been in shortage in spite of abundant sources. The town area has always been affected the most with serious shortage of drinking water. With the increase in population, the problem seems to be aggravating faster than a solution can be thought of. There have been plans to address this issue but these plans have been more reactive than proactive. Ideally the water planning should be done along with the town planning but is there such a thing as town planning in Kalimpong? Well till the time we do have a planning team, something has to be done by the people themselves.
In the past five years, the district of Darjeeling has received an average rainfall of 3234 mm with 2012 receiving the least (2970 mm). For the sake of our discussion, even if we assume that Kalimpong receives 65% of the average rainfall in the whole district, it till comes to a very decent amount of 2100 mm. Let us try and understand what exactly this means and why this is good news for us.
We are interested in knowing how much rain water we can collect in an year. Let us for the sake of easy calculation assume that the area of the roof of a house is 100 square meters. Now, if the average rainfall is 2100 mm which is nothing but 2.1 meters of rain per year,
Let us not get ahead of ourselves and let us for the time being assume that we can harvest 60% of the water. (This could be higher given the fact that the hills have a much less polluted environment and hence we would waste lesser amount of water in clearing the whole system before we start collecting the water.) That would mean we would be able to collect approximately 1,26,000 liters of water. That comes to around 345 liters of water per day. Don't you think for an average household, 345 liters of water is enough for the basic needs?
However, this rainfall does not fall evenly throughout the year but is concentrated mostly during the months between May to September, while the rest of the year receives low or very less rainfall. The dry summer seasons are the most difficult times when many of the smaller streams dry up too.
The idea would be to utilize as much rain water as required during the rainy season and store the rest for the rest of the year. But that is where the difficulty arises. One of the best ways of doing this is ground water recharging, which is basically making an arrangement by which the rain water is allowed to seep into the ground rather than flow along the surface in to the streams.
In the plains, ground water charging helps in increasing the underground water level which can then be extracted during the summers from wells. In the mountains, the ground water usually comes out as springs or "jhora". So if the ground water level is maintained, these jhoras will not dry up in the dry seasons. A number of water reservoirs could be built along the mountain all interconnected such that once the reservoir is full, it's overflowing water would be directed to those below. In populated areas water towers could be built which would automatically fill up without the need of pumps, just by the force of gravity. The only requirement would be to collect the water at a higher area and then transfer it to the towers.
The aim would be to minimize water losses through surface runaway and evaporation. This would also help in decreasing landslides, as one of the reasons for landslides is the removal of the top soil due to flowing water.
Rain water harvesting is a very viable and possible option for the people to solve their water problems and if we move forward in a planned way this is not difficult to achieve. Even now many houses use rain water for daily needs, we just need to make these systems more optimized and efficient.
Join us in our wiki to discuss and analyze optimum ways to harvest rain water in our Water Infrastructure section.
In the past five years, the district of Darjeeling has received an average rainfall of 3234 mm with 2012 receiving the least (2970 mm). For the sake of our discussion, even if we assume that Kalimpong receives 65% of the average rainfall in the whole district, it till comes to a very decent amount of 2100 mm. Let us try and understand what exactly this means and why this is good news for us.
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| Rainfall Distribution chart |
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| Rainfall Distribution for the last five years in Darjeeling District |
We are interested in knowing how much rain water we can collect in an year. Let us for the sake of easy calculation assume that the area of the roof of a house is 100 square meters. Now, if the average rainfall is 2100 mm which is nothing but 2.1 meters of rain per year,
the total volume of rain = total surface area of roof X average rainfall.This comes to 2.1 x 100 = 210 cubic meters of rain. Do you recall how many liters of water is equal to 1 cubic meter? Yes! It's a whopping 1000 liters! So, in a year a single house can collect 2,10,000 liters of water.
Let us not get ahead of ourselves and let us for the time being assume that we can harvest 60% of the water. (This could be higher given the fact that the hills have a much less polluted environment and hence we would waste lesser amount of water in clearing the whole system before we start collecting the water.) That would mean we would be able to collect approximately 1,26,000 liters of water. That comes to around 345 liters of water per day. Don't you think for an average household, 345 liters of water is enough for the basic needs?
However, this rainfall does not fall evenly throughout the year but is concentrated mostly during the months between May to September, while the rest of the year receives low or very less rainfall. The dry summer seasons are the most difficult times when many of the smaller streams dry up too.
The idea would be to utilize as much rain water as required during the rainy season and store the rest for the rest of the year. But that is where the difficulty arises. One of the best ways of doing this is ground water recharging, which is basically making an arrangement by which the rain water is allowed to seep into the ground rather than flow along the surface in to the streams.
In the plains, ground water charging helps in increasing the underground water level which can then be extracted during the summers from wells. In the mountains, the ground water usually comes out as springs or "jhora". So if the ground water level is maintained, these jhoras will not dry up in the dry seasons. A number of water reservoirs could be built along the mountain all interconnected such that once the reservoir is full, it's overflowing water would be directed to those below. In populated areas water towers could be built which would automatically fill up without the need of pumps, just by the force of gravity. The only requirement would be to collect the water at a higher area and then transfer it to the towers.
The aim would be to minimize water losses through surface runaway and evaporation. This would also help in decreasing landslides, as one of the reasons for landslides is the removal of the top soil due to flowing water.
Rain water harvesting is a very viable and possible option for the people to solve their water problems and if we move forward in a planned way this is not difficult to achieve. Even now many houses use rain water for daily needs, we just need to make these systems more optimized and efficient.
Join us in our wiki to discuss and analyze optimum ways to harvest rain water in our Water Infrastructure section.
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