The role of cloud forests as water storages in South America Christof Schneider Water Security and Climate Change Conference Session 10 “Nature Based Solutions for WRM” 18-21 September 2017 Cologne, Germany

Hydrology of tropical montane cloud forests (TMCF) Cloud water interception <5% to >75% of water input (Bruijnzeel et al. 2011) 6% to 60% of water input (Villegas et al. 2008) Low evapotranspiration (runoff coefficient > 0.8; Strauch et al. 2016) High water retention capacities of soils

Value for water resources management High quality water Millions of people depend on water from TMCF Increased stream flows Improved water regulation (cloud affected forests: Mulligan, 2010)

Threats to TMCF Climate change Land-use change

Investment in Watershed Services (IWS)

ClimateWIse project

WaterGAP3 modelling framework (Cover of cloud affected forests: Mulligan 2010)

First analysis: How large is the impact of cloud water on low flows? Change in Q90 low flows due to cloud water interception Sensitivity analysis 5%, 15%, 30% and 45% cloud water input 27 large cities / 118 surface water withdrawal points (CWM, McDonald et al. 2013)

Impact on river flows Definition benefit: >5% increase 8 / 12

Impact at water withdrawal points

Impact on larger cities

Conclusions Sensitivity analysis: TMCF are important water storages in South America 45,000 to 305,000 km river reaches benefit 3-43% of surface water withdrawal points benefit TOP5-cities: Sao Paulo, Florianopolis, Quito, Medellin and Cali Further model developments are required Calculate cloud water interception Need to consider seasonal variations and local characteristics Approach will allow to evaluate: How important are cloud forests as water storages in South America? How will cloud water storages change in the future? What are the impacts on human water supply today and in the future? Better estimation of future water stress in South America Support IWS and nature-based solutions

Outlook What is the benefit of combining grey and green based solutions? Water security Hydropower generation Flood control Carbon sequestration Protection against landslides and soil erosion Biodiversity conservation How can our findings be used in other parts of the world? 41% in the Americas (including Hawaii) 43% in Asia (including northern Australia and Oceania) 16% in Africa What are the fields of future research? Quantify ecosystem services Ecological thresholds for biodiversity loss

Thank you for your attention! contact: schneider@usf.uni-Kassel.de funded by: (German Research Foundation) - FL 396/4-1

Next steps Calculate cloud water interception with WaterGAP3 Seasonal variations Local characteristics: climate, vegetation characteristics, topography f(air flux, liquid water content, area exposed, interception efficiency) Improve estimation of TMCF distribution (current and future) Simulate future impacts Climate change Land use change Socio-economic changes Identify hotspots of risk for future water stress

Literature research Magnitude of cloud water input 7-15% of water input, Kosnipata basin, Peruvian Andes (Clark et al. 2014) 7.4 to 19% of the water input Sierras de las Minas, Guatemala (Holder 2006) 11-30% of water input Kona Hawaii (Brauman et al. 2010, 2012) 30–45% of water input (Dawson, 1998; Holder, 2003; Ritter et al., 2008) 34% of water input, along California coast (Dawson 1998) 37-46% of the water input, leeward Maui (Scholl et al. 2007) 15-30% increase in rainfall (Bruijnzeel and Hamilton 2000) 25-40% increase of water input Canary Islands (Ritter et al. 2008) <5% to >75% of water input (Bruijnzeel et al. 2011) Significant impact at local scale Variations (season, distance to ocean, vegetation structure)