A selectivity index for public-private partnership projects in the urban water and sanitation sector in Latin America and the caribbean.

The rapid urban development, the Agenda 2030, the climate change adaptation and the COVID 19 crisis highlight the need to increase investment in public infrastructure and improve water supply and sanitation services. For this, an alternative to traditional public procurement is the participation of the private sector under the public-private partnership (PPP) model. The objective of this article is to develop a tool based on critical success factors (CSFs) that allows for evaluation during early stages of the convenience of developing a PPP project for W&S in urban areas of Latin America and the Caribbean. The index was developed based on literature review (779 variables), review of cases (20 variables) and expert opinion to assign them an estimated value of importance. The results were analysed by exploratory and confirmatory factor analysis, selecting 17 main variables grouped into 6 CSFs, the most relevant of which are Convenience, Certainty, Leadership, Attraction, Performance and Reliability. The application of this index allows an early assessment of the feasibility of a PPP project and/or the selection of the alternatives with the best chances of success. On the other hand, this study contributes to the international discussion on the most relevant elements related to the success of PPP in W&S projects.

Modelling-based methodological approach to assess the effect of urbanization on hydrology and runoff water quality: a case of study for tropical and dry regions.

It is necessary to have unified tools and methodologies for the correct understanding and quantification of urbanization effects on watershed hydrology. This study presents a modelling-based methodology developed on EPA SWMM to evaluate the effect of urbanization in conceptual watersheds using meteorological data from cities in Spain and Colombia. Results show that the effect of urbanization is significant in variables such as runoff volume, peak flow and pollutant loads, increasing these indicators in all cases. Furthermore, this effect has different dynamics for the regions evaluated. Overall, Colombian cities presented higher runoff volumes, peak flows and pollutant loads, while Spanish cities presented higher variability in these variables due to urbanization. The analysis allowed to cluster the cities within each country, using as criteria the modelled hydrological behaviour. A curve fitting procedure presented high performance rates for all the variables studied.

Sustainable Urban Drainage System (SUDS) modeling supporting decision-making: A systematic quantitative review.

Decision Support Systems (DSS) for Sustainable Urban Drainage Systems (SUDS) are a valuable aid for SUDS widespread adoption. These tools systematize the decision-making criteria and eliminate the bias inherent to expert judgment, abridging the technical aspect of SUDS for non-technical users and decision-makers. Through the collection and careful assessment of 120 papers on SUDS models and SUDS-DSS, this review shows how these tools are built, selected, and used to assist decision-makers questions. The manuscript classifies the DSS based on the question they assist in answering, the spatial scale used, the software selected, among other aspects. SUDS-DSS aspects that require more attention are identified, including environmental and social considerations, SUDS trains performance and criteria for selection, stochasticity of rainfall, and future scenarios impact. Suggestions for SUDS-DSS are finally offered to better equip decision-makers in facing emerging stormwater challenges in urban centers.

A simplified method for determining potential heavy metal loads washed-off by stormwater runoff from road-deposited sediments.

A simplified method is proposed for determining the potential load of heavy metals (HMs) derived from the wash-off caused by surface runoff on road-deposited sediment (RDS). The method consists of three phases: (i) characterization of RDS load wash-off, (ii) assessment of HM load in dry weather, and (iii) application of a wash-off equation. Two processes were included in the wash-off equation: HM transport (solid fraction) and HM leaching (dissolved fraction). The average wash-off of HMs ranges from 16.6 to 46.3%, relative to the total mass of HMs associated with dry-weather RDS (Pb, Zn, Cu, Cr, Ni, Cd, Fe, Mn, Co, and Ba). Cd, Mn, and Zn presented the highest wash-off in the areas studied. The size fraction below 250µm contributed an average of 86.7% of potential HM load washed-off from RDS. Based on the phenomena included in the wash-off equation, it was observed the following order of precedence: transport of RDS<250µm, leaching of RDS<250µm, and leaching of RDS≥250µm. Solid and dissolved fractions contributed 70.7 and 29.3% of the potential HM load washed-off by runoff from RDS, respectively. The proposed method serves as a management tool for road HM pollution during rain.