Planejamento adaptativo de sistemas hídricos urbanos no contexto de incertezas profundas: proposta metodológica

Araújo, Bruna Mattos; Pacheco, Gabriela Cristina Ribeiro; Fernandes, Camila Yarla; Lima, Diego da Silva; Alves, Conceição de Maria Albuquerque

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Scientific/Technical Article • RBRH 28 • 2023 • https://doi.org/10.1590/2318-0331.282320220117 copiar

Planejamento adaptativo de sistemas hídricos urbanos no contexto de incertezas profundas: proposta metodológica

Autoria SCIMAGO INSTITUTIONS RANKINGS

RESUMO

A operação de Sistemas Hídricos Urbanos (SHU) é permeada por incertezas, e frequentemente depende de grandes montantes de investimento, além de exigir o planejamento a longo prazo em contextos futuros com mudanças constantes e alto grau de imprevisibilidade (mudanças climáticas, fatores sociais e econômicos). Vários desses fatores de incerteza carecem de representações analíticas, tampouco contam com amplo consenso entre especialistas acerca da influência que exercem na performance de SHU. A literatura internacional se refere a esse tipo de incerteza como incertezas profundas (DU). Este trabalho propõe uma abordagem generalista para incorporar a influência de incertezas profundas na gestão e planejamento de três categorias de SHU: 1) Sistemas de Abastecimento de Água; 2) Sistemas de Drenagem; 3) Sistemas de Aproveitamento de Água de Chuva. A abordagem proposta define etapas para seleção das políticas mais adequadas para cada sistema e para avaliação dessas estratégias em uma ampla gama de cenários. As particularidades de cada sistema levam a ajustes na estrutura geral da abordagem proposta. A abordagem foi aplicada para um Sistema de Aproveitamento de Água de Chuva na cidade de Ipameri no estado de Goiás, Brasil. Os resultados destacam a influência dos fatores de DU no desempenho dos sistemas e atestam a contribuição da metodologia para o planejamento adaptativo de SHU.

Palavras-chave:
Incertezas profundas; Planejamento adaptativo; Sistemas hídricos urbanos

Urban Water System	Objectives
Urban Water Supply System	- Maximization of reliability, calculated as the percentage of years when the water storage dropped below some percentage of its maximum capacity;
	- Minimization of restriction frequency, represented as the number of years when water restriction measures were applied;
	- Minimization of new Infrastructure Net Present Value (INPV);
	- Minimization of the cost of short term risk mitigation instruments;
	- Minimization of Worst First-Percentile (WFPC) of financial variability caused by drought management actions (restrictions and transfers) among all realizations.
Urban Drainage System	- Minimization of surface runoff volumes and peak flow;
	- Minimization of pollutant loads from the different types of land use;
	- Maximization of avoided costs;
	- Minimization of system costs (infrastructure and maintenance).
Urban Rainwater Harvesting System	- Maximization of the water demand served, taken as a percentage of non-potable demand;
	- Maximization of reliability, represented by the number of days that water demand is fully served;
	- Maximization of rainwater harvested, calculated as the percentage of the total rainwater volume collected that is actually used;
	- Maximization of Net Present Value of the URHS including a balance between costs and benefits (water tariff savings) of the system;
	- Maximization of Net Present Value per volume of consumed rainwater;
	- Maximization of Cost-Benefit Rate.

Application	Deep Uncertainty Factor
Urban Water Supply System	- New investment discount rate;
	- Water tariff;
	- Effectiveness of water consumption restriction;
	- Time to issue environmental licenses for infrastructure construction;
	- New infrastructure construction costs.
Urban Drainage System	- Stakeholder preferences;
	- Rate of land parceling and overall imperviousness;
	- Land use change;
	- Household use of Low Impact Development (LID) solutions (user cooperation);
	- Effectiveness of selected LID solutions;
	- New investment discount rate.
	- Rate of increase in operational and maintenance costs along the simulation.
Urban Rainwater Harvesting System	- New investment discount rate;
	- Water tariff;
	- Increase rate in operational and maintenance costs along the simulation;
	- Demand (potable or non-potable).

Application	Well-Characterized Uncertainties
Urban Water Supply System	- Evaporation rates in the reservoirs (water sources);
	- Streamflow (inflows) into the water sources;
	- Future water demand.
Urban Drainage System	- Historical rainfall data.
Urban Rainwater Harvesting System	- Historical rainfall data.

Application	Policies
Urban Water Supply System	- Short-term actions: water transfers, water consumption restriction, contingency water tariffs, educational campaigns towards rational water use. These are mostly drought mitigation actions.
Urban Water Supply System	- Long-term actions: new infrastructures or infrastructure expansion in the water system and network (reservoirs, pumping, water treatment plants).
Urban Drainage System	- Large scale: long-term planning of land use, LID solutions in public areas.
Urban Drainage System	- Small scale: individual LID solutions in household (land parcels).
Urban Rainwater Harvesting System	- Small scale: different configurations of the system in terms of water demand and rooftop area.

Associação Brasileira de Recursos Hídricos Av. Bento Gonçalves, 9500, CEP: 91501-970, Tel: (51) 3493 2233, Fax: (51) 3308 6652 - Porto Alegre - RS - Brazil
E-mail: rbrh@abrh.org.br

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[1] E-mails: bruna.mattos.araujo@gmail.com (BMA), gabrielacrpacheco@gmail.com (GCRP), camilayarla1@gmail.com (CYF), diego.lima@ifal.edu.br (DSL), cmaalves@gmail.com (CMAA)