“The Vital Few and The Water Benefit Calculator” by Derek Schlea and Paul Hicks at the 2023 Water for Food Global Conference. A recording of the presentation can be found on the conference playlist: https://youtube.com/playlist?list=PLSBeKOIXsg3JNyPowwJj6NDSpx4vlnCYj.

1. Session: Sustainable solutions to water and
climate challenges
The Vital Few and
The Water Benefit Calculator
Derek Schlea - LimnoTech
Paul Hicks – Catholic Relief Services

2. El Salvador’s Water Crisis
El Salvador needs healthy coffee forests
to protect its water sources for the future.
El Salvador is one of the most water insecure countries in Latin
America, facing several threats.
The biggest threat to water resources is land degradation, and
the primary cause of land degradation is unsustainable
agricultural practices.
Most remaining forests in El Salvador are coffee farms, where
coffee is grown under tall shade trees. These coffee agroforestry
systems are the headwaters for many of the country’s rivers and
streams.
The way coffee is produced and processed can either be part of
the solution to the water crisis or it can be part of the problem.
90%
of streams are too contaminated
for human use
40%
of Salvadorans do not have
access to safe and reliable
water
30-70%
loss of dry-season flows in streams
and rivers in the last 30 years
2

3. 3
In 2014, The Nature Conservancy carried out a study of 500
cities around the world. They concluded that the most cost-
effective way to protect water sources is to promote
sustainable agriculture in critical watersheds.”
Good agricultural
practices
=
Good watershed
management
“The greatest potential
to secure water for cities
lies in improving the
management of
agricultural lands…”

4. Question:
What are the few agricultural practices that are most
effective at reducing runoff/erosion and maximizing
water recharge on coffee farms?

5. Water Benefit Calculator: Goals and Objectives
• The WBC was intended for the coffee growing
community to support farm decision-making
related to water and sediment conservation
• Objectives included quantification of
hydrological benefits from common practices
implemented through the Blue Harvest project
and gathering cost data to identify the
following:
1. Prevalence and cost of implementation of
practices in Central American countries
2. The mix of practices that generate the
highest hydrological impact
3. Practices that provide the largest
hydrological impact for the least cost
Who are WBC users?
• Land managers and extensionists
who wish to prioritize interventions
based on potential hydrologic impacts
• Private and public sector actors
seeking to invest in improved water
resource management and
understand the potential returns on
their investment

6. • Started as a spreadsheet tool
• Finalized as a web-based tool
• Represents hydrologic cycle at the
farm/field scale along a hillslope
• Simulates water balance components
and sediment loss from upland erosion
• Compares baseline conditions against
conservation scenarios (land cover
changes, interventions)
Water Benefit Calculator: Details

7. Water Benefit Calculator: Details
• Framework built using HSPF – the
Hydrologic Simulation Program
FORTRAN
• Mechanistic, process-based model:
• Vegetative cover
• Canopy interception
• Infiltration
• Surface ponding
• Storage in upper and lower soil layers
• Routing of water along a transect
• Evapotranspiration
• Surface runoff
• Subsurface flow (shallow interflow and
baseflow)
• Soil erosion/sediment yield
• Hourly simulation timestep, with
output reported as average annual
• Daily output exporting capability for
diagnostic purposes

8. Water Benefit Calculator: Central America
• An initial application focused on
six (real-world) coffee farms in El
Salvador
• Rio Refugio subwatershed,1.1km2
• Spatially explicit with
representation of unique
topographic features
• Simulated without- and with-
interventions including
• Infiltration trenches
• Terracette planting
• Shade species and ground cover
• Live barriers

9. Water Benefit Calculator: Central America
• A second application expanded to
farms in Honduras and Nicaragua
• Also sought to quantify
prevalence and costs of practices
in each location
• Among most common and least
costly practices were ground
cover and shade tree planting

10. Water Benefit Calculator: Ethiopia
• Desktop-based version (due to
internet/remote connectivity issues)
• Funding from United States Agency for
International Development (USAID)
• New crops and interventions
• Intended to travel to Ethiopia for both site-
specific data collection and hosting training
sessions (…but the pandemic…)

11. Water Benefit Calculator: Ethiopia
• Enhanced the hierarchy and
model structure
• Added a cost-benefit module that
factored in crop production costs
and revenue
• Included a calibration phase
• Intended on collecting site-specific
measurements
• Instead used literature/research-
based calibration approach to ensure
reasonableness of water balance and
sediment yields

12. Water Benefit Calculator: Lessons Learned
Advantages & Successes
• The WBC can be tailored to the needs of
the individuals and location where it is
applied while using best available
information and well-established
modeling techniques.
• It is relatively simple to apply with few
input requirements and easy to follow
instructions.
• The WBC can provide valuable information
regarding hydrologic and water quality
benefits of existing and planned future
management interventions.
• Coupled with other, on-the-ground
research and information, the WBC was
used to help identify “the vital few”.
Limitations & Recommendations
• Prior to any decision support tool
development effort, critical thinking and
information gathering as part of a well-
planned process is recommended to ensure
the tool meets intended end users needs.
• Realistically, who will be using the tool?
• What information or value are we providing?
• The lack of location-specific field data to
calibrate to is an area of uncertainty for
the WBC or similar tools.
• Ensuring reasonableness of results is a critical, but
often overlooked aspect.
• There is more to it than understanding the
costs and benefits of interventions
• Cultural, social, and political influences
• Practicality, ease of installation or adoption

13. Question:
What are the few agricultural practices that are most
effective at reducing runoff/erosion and maximizing
water recharge on coffee farms?
Keep it simple:
Training and extension get exponentially complex with the number of
new farm practices we introduce to farmers.

14. Wilfredo Garcia, farm manager at the Noruega Farm, Apaneca
Cover crops:
a “simple” solution
We promote cover crops as soil cover, green manure, and
to increase soil organic matter (and soil carbon).
How do they it impact erosion and water recharge?

15. Jack bean (canavalia) planted as cover crop (green
manure) between rows of coffee plants.

16. Coffee farm with
cover crops
Coffee farm without
cover crops

17. We have been measuring run-off
and erosion from side-by-side
erosion plots in coffee and maize
farms for three years (2020 to
2023).
(Erosion plots were designed by
CIAT/Bioversity)
We collect water and soil in 50-
gallon barrels after every storm
event.
Plot with
cover crops
Plot with no
cover crops
Cover crops dramatically
reduce water run-off
and erosion

19. Keep soils covered with cover crops and
crop residues
Conclusion:
The agricultural practices most effective at reducing
runoff/erosion and maximizing water recharge on farms are:
Plant live barriers along contours
(ideally leguminous plants, bushes or trees)
1
2

20. Coffee Training Center
The RENACER Coffee Training Center trains and
supports coffee farmers and cooperatives to renovate
coffee farms by applying sustainable and cost-
effective practices.
RENACER received the 2023 Sustainability Award
from the Specialty Coffee Association
www.blueharvest.org
Professor Sigfredo Corado, Director, RENACER Coffee School

22. • Derek Schlea - dschlea@limno.com
• Paul Hicks – paul.hicks@crs.org