Dating back 200 years, tribes in northeast India have used bamboo drip irrigation as a means of bringing water to seasonal crops. Tribal farmers of the north-eastern part of India, in the state of Meghalaya, have been using an indigenous technique of bamboo drip irrigation to irrigate their plantation crops. These farmers of the Jaintia and Khasi hill areas have developed this system of tapping springs and stream water to grow betel leaves, black pepper and arecanut.
The bamboo drip irrigation system is based on gravity and the steep slopes facilitate in implementing it. Water from an uphill source is tapped and brought to the plantation by a main bamboo channel. Usually these water sources are far off from the plantations and the main bamboo channel runs hundreds of meters — in some cases even a few kilometers. The water is then regulated through a complex bamboo network of secondary and tertiary channels to all the parts and corners of a plantation, right up to the bottom of the hill. An assortment of holed bamboo shoots zig-zag downhill, diverting the natural flow of streams and springs across terraced cropland. The advantages of using bamboo are two-fold: it prevents leakage, increases crop yield with less water, and makes use of natural, local and inexpensive materials.
The topology of the region is hilly with steep slopes and rock boulders. The soil depth on these hills is low and has poor water retention capacity. Though the region gets plenty of rain during the monsoon season, irrigation becomes a necessity during the dry season. The terrain imposes a challenge in bringing the water from distant water sources to the plantations. Diverting water through ground channels is not possible. Faced with this need for water, and the challenges imposed by the terrain, the tribal farmers came up with this unique irrigation system.
The few materials needed are a small dao (a type of local axe), bamboo strands of various sizes, forked branches, smaller bamboo shoots used for the channel diversions, and two willing labourers. Bamboos of varying diameters are used to build the channels, support structures, diversion pipes and strips. Channels are held above the ground by bamboo or wooden Y shaped sticks. One stretch of channel is lashed to another by thin bamboo strips. Indigenous tools like a dao, a type of local axe, and chisels of various shapes and designs are used to build the bamboo network. Two labourers can construct a network covering 1 hectare of land in 15 days. They are built with such skill that water wastage by leakage is minimal. The construction is based on a simple rule of thumb — the ratio of diameter of primary channel to tertiary channel determines the quantity of water which will reach the trees. It is a subtle skill which comes with years of observation and experience.
To get started, locate an available water source. Next, select a sloped area of land (at least 30 meters in variation). Then slice the bamboo shoots and forked branches, placing the wider shoots in the first channel and the smaller pipes for the last section (plan for 5 stages). Puncture a series of holes in the shoots, spacing them equally. Ground clearance should progressively descend so that the water may be dropped near the roots of plants in the last section (10-15 cm above ground). To reinforce the structure, tie the pipes and forked braches together using fibre-rich twine as rope. At points of diversion, smaller bamboo shoots may be used to redirect water.
Materials used during installation last around three years, while maintenance is limited to cleaning and reinforcement after seasonal monsoons. Cost is also limited to labour, which can be carried out by farmers themselves. This traditional water structure is indeed contextual to location. Such variables include: replenish able supplies of bamboo, upland sources of water, and the presence of traditional terrace agriculture. Adapting to drier growing seasons, farmers are advised to match irrigation decisions with crop selection. Professor Raman than of Tamil Nadu Agriculture University suggests that “during the June to September season … stop cultivation of rice and opt for crops such as pulses, sunflower, sesame and maize. In areas affected severely by drought, [farmers] should go for pearl millet, minor millet and forage crops. However, in places where there is water stagnation, they can continue to grow rice.
In the Meghalaya hills there are an estimated 3,108 square kilometers of bamboo forests. In 1990, it was estimated that the total yield of bamboo in the state was 2.09 tons/hectare/year. The 38 different species of bamboo in the region are typically harvested at the community level and loosely managed by the Autonomous District Councils (ADC). Bamboo supplies have recently come under threat from a surge in rodent populations, gregarious flowering, disease, and large-scale extraction.
Nonetheless, large-scale conservation and protection plans are underway in Arunachal Pradesh, Assam, Manipur, Meghalaya, Nagaland, Mizoram, Tripura, and Sikkim, which together contain over 50% of India’s bamboo supply within 226,000 square kilometers of land. The Jaintia, Khasi, and Garo hill tribes have long entrusted the use of bamboo drip irrigation as a means to fulfilling domestic, agricultural, and customary needs. Its function remains unspoiled as the rains continue to fall and the bamboo continues to grow.
The cost involved in building the system is minimal. Bamboo is available freely in this region. Usually the farmer himself sets up the system in his plantation with some help from one or two labourers. The region gets heavy rain, so as a result each installation lasts for about two-three years. After the rainy season the undergrowth is cleared and reinforcements are provided. Old bamboo is left to rot, which over time returns to the soil as humus. Cooperatives are formed and each farmer provides his skill and labour to build and maintain the system. The distribution of water from one plantation to another is done by diverting water at fixed timings. This avoids the occurrence of conflicts between various farmers. By this method the whole community works harmoniously — sharing the limited resources judiciously.
The good thing about this system is it doesn’t need any fuel or power. One can consider implementing it in regions where bamboo is available for free or at a low cost. One notable drawback is that bamboo starts to rot in rain, so the whole network needs to be rebuilt after two-three years. Overall it looks to be an economical and sustainable irrigation system which can be set up for farm needs or for an urban permaculture garden.
(The views expressed are personal)
