Ecological Flow Deficit in a Context of Institutional Rigidities and Climate Change: The Case of Mapocho Alto, Central Chile

What is it about?

This study aims to determine current and future ecological flow deficits using two indicators: the accumulated water volume deficit and the frequency of runoff falling below ecological flow thresholds. Given the absence of defined ecological flows in some basins and uncertainties about future water system operations, an original methodology tailored to the Chilean context is proposed. The conclusions underscore the necessity of addressing institutional constraints, such as static ecological flow definitions, to prevent severe ecosystem issues in basins where runoff is projected to decline while demand remains constant or increases, a concern applicable to other countries with similar institutional frameworks.

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Why is it important?

The results of this work have shown that water regulation in Chile is unable to safeguard ecological flows in the analyzed basins of the Mapocho Alto River system. In all these basins, deficit volumes have been calculated for the historical period of 1985–2020, and—using runoff projections for climate change—are also foreseen for the future (the 2030–2050 period). The deficit values obtained, unlike in previous works, consider an estimate of the ecological flows in sub-basins, a simulation of the operation of the system, and an exhaustive compilation of water use rights (not only those available in the database of the DGA). This makes our estimates more reliable and representative of the reality in the specific water system under study. A paramount problem in the area of analysis of this study, and in Chile in general, is the fact that the exercise of most (or all) water use rights is not limited by appropriately determined, enforced, and safeguarded ecological flows. This corresponds to an important limitation of the institutional structure of Chile´s water regulation system; according to the results of this study, this limitation could have a very significant future impact on the Arrayán en la Montosa (ALM) basin. Moreover, the methology we use can be apply to other countries depending on data availability.