Water Yield
The Valley of Grace BioHub’s primary bankable service: catchment restoration in the below-dam Riviersonderend corridor to increase usable water yield for the Western Cape Water Supply System.
Service Description
The below-dam corridor runs approximately 90 kilometres from the Theewaterskloof Dam wall to the Breede River confluence near Swellendam. This corridor currently carries no equivalent to the Greater Cape Town Water Fund’s above-dam clearing programme.
Four Water Retention Landscape mechanisms deliver the yield:
- Alien clearing on hillslopes and riparian zones
- Soil sponge restoration through fynbos and renosterveld recovery, functioning mycorrhizal networks, and riparian corridor repair
- Water-efficient agriculture and agroforestry
- Distributed water storage through farm dams, restored wetlands, and on-farm water harvesting
Evidence Base
Van Wyk (1987) documented a 55% streamflow reduction in fynbos catchments 23 years after pine infestation. [IC]
Le Maitre et al. (2019) modelled that current invasions reduce WCWSS assured yield by approximately 38 million m³/year, rising to approximately 130 million m³/year in 45 years without clearing. [IC]
Van Wilgen et al. (2008) estimated total invasive-related runoff reductions in fynbos and grassland biomes at levels significant to national water security. [IC]
Target Financial Instrument
Cape Water Performance-Based Bond (FR31PB), JSE-listed April 2026, ZAR 2.5 billion. The bond is designed as the first in a replicable series covering South Africa’s Strategic Water Source Areas. Performance payment is contingent on independently verified invasive-clearing and water-yield outcomes.
See FR31PB Alignment for the full alignment documentation.
Readiness Status
Contractable after build-out. Required before tender:
- Verification-ready restoration inventory at landscape scale
- Landowner stewardship agreements authorising the work
- Monitoring architecture aligned with Conservation Alpha methodology
- Convening structure capable of executing at required tempo
Gap Register
- SWSA designation confirmation for the Valley of Grace operational scope [TBV against Le Maitre et al. 2018 WRC report]
- Conservation Alpha methodology alignment not yet initiated
- Landowner stewardship agreement programme not yet operational