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Calculating Water Benefits on Coffee Farms

2016-06-23 Comments Off on Calculating Water Benefits on Coffee Farms

This a guest post by Will Garde, from the Caffeinated Engineer,  who has provided technical support to CRS’ Blue Harvest program this past year.

Photo by Will Garde

Photo by Will Garde

Knowledge-based Coffee Watershed Management

We know a lot about sustainable agricultural practices, and the specialty coffee industry has been a pioneer in incentivizing farmers to adapt good practices. But these practices, require time and money, which most smallholder farmers can scarcely afford. So a critical question is:

What agricultural practices provide the biggest positive benefits for the environment?

To respond to that question, CRS’ Blue Harvest program has been working with LimnoTech to design and test the Water Benefits Calculator. (I contributed to this team, with background research and technical input).

The WBC is an interactive tool designed to give farmers and decision makers the ability to quantify how certain agricultural practices increase water retention and decrease soil erosion. The goal of the WBC is to help farmers prioritize the most effective practices to improve soil and water management to improve farms, and to increase water availability downstream for water users, particularly drinking water supplies.

A beta version of the Blue Harvest WBC was presented as a poster at the SCAA 2015 event in Atlanta. Here is a brief explanation.


How was the WBC developed?

Building from LimnoTech’s vast work on designing tools quantify water benefits (such as Coca-Cola’s Replenish tools), the Blue Harvest WBC is grounded on a well-established engineering framework.

The WBC was developed at a pilot scale in the Rio Refugio microwatershed (1.1 km2) in El Salvador in 2015 and 2016. Field data was gathered from six farms in watershed and this data was used to model potential farm water retention and decrease in soil erosion.

The WBC gives decision makers the ability to analyze different water and soil conservation strategies by comparing water retention and soil erosion before and after implementing farm interventions. WBC users start by inputting several key farm characteristics, such as hillside slope, farm size, canopy cover, rainfall, etc. and the WBC uses these characteristics as a baseline to calculate the potential impact of interventions. Users can then pick and choose which interventions to include in their analysis dependent on what is appropriate and practical for their farm.

Currently, the WBC interventions include: infiltration ditches, terracette planting, shade species planting, hillside live barriers, and staggered terracette planting.

Some quick definitions:

  • A terracette and staggered terracette planting are planting patterns that disrupt water runoff and increase infiltration.
  • Hillside live barriers are walls of vegetation planted along contours that disrupt water runoff and give it time to infiltrate into the soil. These barriers also act as a natural wall to retain soil.
  • Infiltration ditches are shallow ditches dug along contours that capture water and soil as they run-off a slope, thereby reducing erosion and allowing water to infiltrate into the subsoil.
  • Finally, planting shade species increases rainfall interception, which decreases soil erosion.


The Next Steps?

CRS and LimnoTech are starting to create a full, web-based, open-access version of the WBC, with funding from the Inter-American Development Banks and its SAFE Platform.   Blue Harvest is working to add more interventions and a cost function associated with those interventions. That way, decision makers would also have a price tag attached to each scenario of interventions. The goal is for the Blue Harvest WBC to serve as a robust decision-making and modeling tool applied to many different coffee growing regions.

— Will Garde