Rebelo, A.J., Holden, P.B., Esler, K.J. and New, M.G. (2021). “Benefits of water-related ecological infrastructure investments to support sustainable land-use: a review of evidence from critically water-stressed catchments in South Africa.” Royal Society Open Science.
The review combines a framework of intervention effects, peer-reviewed and grey literature, and a causal loop diagram for the Berg, Breede and uMngeni catchments, and calls the evidence for benefits “empirically weak”. It asks for baseline data before interventions and monitoring during and after them. The wiki cites it as the clearest statement of the evidence gap a retention program has to close.