|Anno Farms - Ethiopia - perennial spring flow|
Saturday, December 14, 2013
Groundwater is being depleted at unacceptable levels in countries like India, China, and the US; there are many culprits, but the most significant is the drawdown of groundwater by farmers. In India this is at a rate of up to 1 meter a year! Anecdotally and from observations we know that where vetiver grass hedgerows are in place groundwater is more reliable due to increased recharge as is shown in India where ephemeral streams flowing longer into the dry season, and wells with constant supplies of water (compared to dried up wells where there is no vetiver). In Ethiopia, on a commercial 500 ha farm with 250 km of vetiver hedgerows, not only crop yields increased but also erratic springs ran at a constant flow throughout the year with potable drinking water (note the vetiver hedgerows would also have likely removed most of the potential contaminants that would otherwise have contaminated the groundwater).
There are two research papers that I recommend that you read. The first one “Vetiver Potential For Increasing Groundwater Recharge” by B. Deesang et al (2006) describes what happens to rainfall run off with the following result “The results showed that runoff accounted for 3-13 % of rainfall at study sites while vetiver hedgerows reduced runoff by 19-56 %. Evapotranspiration, soil-water storage, and deep drainage accounted for 33-67 %, 0-14 %, and 31-65 % of rainfall respectively. The vetiver hedgerows increased groundwater recharge by as much as 20 %”.
The second paper “Modeling Ground Water Recharge under Vetiver Hedgerows” by K. Vinod Kumar (2011) addresses why vetiver does such a good job for groundwater recharge. We know that a mature and well planted vetiver hedgerow backs up rain water and releases it slowly and at the same time spreads it out so that the crops below the hedgerow benefit from the extra moisture. The modeling done by Kumar found “that the preferential flow as laminar film on the dense vertical roots of vetiver is the most important contribution of vetiver for ground water recharge, directly through increased fast infiltration and indirectly through absorbing the backwater when the rain has stopped.” I would add that vetiver roots are deep and often break through hard-pan to further enhance groundwater recharge.
More research needs to be carried out under different climatic and soil conditions. But the point is vetiver does enhance significantly groundwater recharge and this includes “flat” land. Most people don’t see erosion as a problem on so called “flat” farm land – but believe me its there! Vetiver hedgerows would do much to enhance groundwater recharge in the “flat” irrigated areas of India and Pakistan. At the same time the phytoremedial action of vetiver would reduce excess agrochemicals and wastewater that are playing havoc with the health of farmers through the contamination of groundwater that farmers pump and drink. Research by Sylvie Marcacci “A Phytoremediation Approach To Remove Pesticides (Atrazine And Lindane) From Contaminated Environment” (2004) is a good example.
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