THE VETIVER SYSTEM – AN OVERVIEW
Introductory photo essay: VS_Overview v2.pdf (vetiver.org)
VETIVER GRASS TECHNOLOGY. (VGT) is low cost, effective and easy to apply. It is centered on the multi-applications of Vetiver grass (Chrysopogon zizanioides). There are many uses covering a wide range of activities in which problems are solved. Some of the general use areas concern agriculture, slope stabilization, contaminated land and water, disaster mitigation, as well as other uses such as carbon sequestration and handicraft production. This website presents, in a systematic way, information that a VS user would need in order to address problems they face, wherever they may live and work. Its use across the globe will mitigate some of the negative impacts of climate change.
The following are the critical elements that define vetiver’s basic as a narrow stiff grass hedge (barrier).
“Narrow stiff grass barriers (hedgerows) when placed across the slope of the land, if applied correctly, create the means of reducing sheet, rill and ephemeral gully erosion by trapping sediment and spreading the concentrated flow of high velocity rainfall runoff (Dabney 1996). Stiff Grass Hedges (SGH) such as vetiver can do this because they can withstand high water flows (40mm deep) and velocities (as much as 0.04 m-3sec-1m-1) and can continue to perform with the buildup of sediment behind the hedge, whereas shorter and softer vegetation will fail and become inundated. Over time the sediment buildup behind the hedgerows changes the slope of the upslope land further reducing flow velocity and increasing the spreading and back ponding effect. Meyer (1995), using a flume study of Vetiver and Switch grass (Panicum virgatum), concluded that SGH have great potential for retarding concentrated overland flows and runoff, and trapping sediment … grasses like vetiver that can retard both low and high (40 cm) flows are thus the most effective….”
“Kervroëdan (2018) investigated composition of narrow vegetative barriers (hedges) for sediment control in France concluded that SGH efficiency depended on hydraulic roughness reflected by stem and tiller density, stem stiffness, and leaf density. Vetiver was not part of the evaluation, but has all the positive traits that makes a good SGH, having dense tillers and stems that work with low flows, and leaves and stem that are stiff and dense that provide the necessary hydraulic roughness at high flows…”
“The other important primary function of the SGH is to increase the infiltration rate of rainwater. Studies indicate that there is a significant increase in infiltration due to large, dense and deep roots, and large soil pores with respect to SGH grasses, Dabney (1996). This increased infiltration results in reduced runoff. A study by Rachman (2004) indicated that hydraulic conductivity within the hedgerow (130 mm h1) was 7 times more than in comparative row crops maize (18 mm h1), and 24 times more than in the fully saturated adjacent sediment deposition area (5.4 mm h1) immediately upslope of the hedge”. In effect a vetiver hedge acts as a very safe vertical drain, directing part of the flow for groundwater recharge, and the balance spread evenly through the hedge to downslope land. — If this is understood, then the need for fully formed and dense hedgerows, as discussed in the November newsletter, becomes more apparent, and is an essential component of a quality vetiver application.
The ability of SGH, in our case vetiver, to spread high velocity rainfall runoff flows; to significantly improve the rate of rainwater infiltration; and to trap eroding soil (and the contaminants that are attached to the soil particles) makes vetiver (along with all its other attributes) a good choice to help correct watershed hydrological imbalances. Correcting the water balance also results in improved soil moisture, a necessity for the improvement of soil microbial activity and soil health generally
THE GLOBAL HYDROLOGICAL CYCLE AND VETIVER: The destabilizing of the Global Hydrological Cycle (GHC) by global warming is the missing topic in climate change discussions. This destabilization is causing the steady increase in the frequency of natural disasters, and in particular drought and flooding. To address this, interested parties (most often policy generators) working on soil, water, pollution, global warming, Net Zero, the Freshwater Boundary, finance, and other related activities should include the dependence and influence on GHC in their research and projects. The object being to create focus on water and land management as key to environmental security and sustainable survival. Vetiver addresses, across sectors, all of the above, particularly impacting on water quantity and quality, and in the process in many cases restoring soil health. Most countries with tropical and semi arid climates will/are being severely affected by GHC changes, and will need to use all opportunities to mitigate drought and flooding. In many regions rivers, lakes and aquifers are at an all time low; cities, towns and villages are either without drinking water, or with water rationing, AND in many instances the quality of the water that is available is seriously contaminated. The Vetiver System with its capacity to manage rainfall precipitation runoff, particularly for the recharge of essential ground water, and in some cases moving it to where it is most needed, thereby steadying Freshwater Boundaries, AND with the capacity to reduce the contaminates (especially those generated by the agricultural sector) that lower water quality, should be seen as one of the most practical and efficient means of mitigating these problems, and should be promoted as such. Our available water mass is dependent on, and is a reflection of how we manage (mostly mismanage), our land. This book – “Water A Reflection of land Use” — published by the Swedish Natural Science Research Council provides a useful background and benchmark to the topic and can provide the basis for action. — https://www.ircwash.org/sites/default/files/Falkenmark-1999-Water.pdf