Flow regime recovery compensation mechanisms in over-built river basins

Abstract:

The natural flow regime in rivers is responsible to define and sustain riverine ecosystems. For many migratory fish species, the recruitment success depends on the synchronization between the hydrologic flow regime and the reproductive cycle. However, in over-built basins, specially hydropower-dominated ones, where reservoirs capture both low and high flows for energy generation, the modification of the natural flow regime disrupts the natural equilibrium, threatening biodiversity and the provision of ecosystem services. Studies have long been carried to understand the response of critical components of natural flow regimes on riverine species (magnitude, frequency, duration, timing and change), allowing their explicitly incorporation in water management decision models besides the traditional scope that emphasizes water quantity (usually limited to a minimum flow). While bringing this concept to operation of water infrastructure systems is a growing consensus worldwide, it still imposes challenges for policy making and implementation, especially when tradeoffs involving other objectives (e.g. hydropower) are present. In complex, multi-reservoir, multi-objective systems, such trade-offs are often poorly known and still lack cost-sharing mechanisms/instruments, which are key to the negotiation and implementation of the required operational changes. This study fulfills both gaps by integrating flow regime recovery into a multi-reservoir system operation in order to draw a tradeoff curve and support cost-sharing mechanisms. The methodology is divided in three parts. In phase (1), multiple flow regime scenarios are incorporated into a dual stochastic dynamic program (SDDP) that simulates and optimizes multi-reservoirs operation. In (2), the trade-offs between the ecosystem recovery (biomass and biodiversity) and the costs of the adaptation (hydropower reoperation) are computed. In (3), a cost-sharing mechanism is proposed based on energy-market configuration. The Upper Paraná River Basin, Brazil, is chosen as study area, which includes 53 hydropower plants distributed in cascade and represents a power capacity of 41,700 MW.