Biophysical Benefits Simulation Modeling Framework for Investments in Nature-Based Solutions in São Paulo, Brazil Water Supply System

Abstract

In order to understand the hydrological impacts of the nature-based solutions in the Cantareira Water Supply System, this study evaluates six different land cover and land use change scenarios. The first and second consider the restoration of native vegetation in riparian areas, the third prioritizes restoration sites using biophysical characteristics (optimized restoration scenario derived from Resource Investment Optimization System—RIOS), the fourth considers best management practices and the fifth and sixth are hypothetical extreme scenarios converting all pasture to forest and vice versa. Two hydrological models were developed to represent the distributions of water and yields in the study watershed: HEC-HMS and SWAT. Simulation results indicate that when nature-based solutions are implemented, surface runoff is reduced and ambient storage increases during the rainy season (December–March); while the overall flow increases during the dry season (June–September). The combination of specific hydrologic components of RIOS-customized intervention scenario simulation outputs—namely surface flows and groundwater contribution to stream flows—indicate on average 33% increase in the overall water yield, or 206 hm3/year, across the study watershed when comparing against the baseline conditions. In the same modeling scenario, the water storage in the sub-watersheds adjacent to the reservoirs showed an increase of 58% (or 341 hm3/year). The results indicate that adopting NbS in the source watershed can mitigate the impacts of extreme drought conditions and contribute toward building long-term water security.

Economic Cost of Drought and Potential Benefits of Investing in Nature-Based Solutions: A Case Study in São Paulo, Brazil

“…Logar and Bergh [19,20] consider the gross domestic product (GDP: the mark Using the results of hydrological modelling analyses for the CWSS [17], we assess the potential economic benefits of NbS investment using estimated avoided income losses from the 2014-2015 drought event. We then conduct a cost-benefit analysis (CBA) to assess the economic viability of NbS investments in CWSS.…”

“…The hypothetical NbS scenario used in our analysis and its modeled impact on the hydrologic behavior of the CWSS-sourced watersheds is presented in Acosta et al (2023) [17]. Table 2 shows the impact of the NbS scenario on the annual combined available surface flows (the sum of surface flows and groundwater-to-stream flows) in the CWSS, as estimated using the Soil and Water Assessment tool (SWAT).…”

“…• SURFGRDw t,baseline : sum of water flow components-surface flows and groundwater to stream flows in hm • SILV p : silviculture production in municipalities in Cantareira system (m 3 /year) from the annual survey PEVS (IBGE). Note: Source: [17].…”

“…Our CBA of NbS investment in the CWSS considered the estimated full-lifecycle costs of the NbS intervention scenario, specifically, of restoring 32,085 hectares distributed across the four subwatersheds [17], as well as the value of increased water availability for the industrial and water sectors, and carbon sequestration. As discussed previously, other benefits were beyond the scope of our CBA.…”

“…In order to fill this gap and assess the economic rationale for investment in NbS as a drought resilience measure, this paper examines the economic cost of the drought to industry and to the water supply and sewage sectors and estimates the potential benefits of investments in NbS in the CWSS (Figure 1). economic rationale for investment in NbS as a drought resilience measure, this pa amines the economic cost of the drought to industry and to the water supply and sectors and estimates the potential benefits of investments in NbS in the CWSS (Fi Using the results of hydrological modelling analyses for the CWSS [17], we as potential economic benefits of NbS investment using estimated avoided incom from the 2014-2015 drought event. We then conduct a cost-benefit analysis (CBA sess the economic viability of NbS investments in CWSS.…”