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The Nature Conservancy and WWF are participating in Mexico's national multi-agency technical working group, commissioned by the National Water Commission (Comisión Nacional del Agua, CONAGUA), the government agency responsible for stewardship and development of the country's water resources, to formulate a national technical standard (Norma PROY-NMX-AA-000-SCFI-2010) for setting environmental flows for the country's waterbodies.  The CONAGUA recognised the need to invest in safeguarding the long-term sustainability of its water resources, particularly in the face of the documented continued deterioration in river ecosystem health and associated benefits for people countrywide.
The Norma, currently drafted and under internal review by CONAGUA (PROY-NMX-AA-000-SCFI-2010), is linked to the Norma Oficial Mexicana, NOM-011-CONAGUA-2000, used to calculate basin water availability under Mexico's National Water Law.  It proposes a four-level hierarchy of methods for determining environmental flows, from planning (Levels 0 and 1) to comprehensive levels (Levels 2 and 3).  The proposed methods range from simple desktop hydrology-based to detailed interdisciplinary assessments, to match the sophistication of flow recommendations to available resources and capacity, ecosystem importance and condition, and the anticipated extent of hydrologic alteration with water resource and infrastructure development. Not only focused at individual site or project level, the standard also incorporates locally tailored procedures to apply the Ecological Limits of Hydrologic Alteration (ELOHA) framework for regional assessment at a basin or supra-basin scale.
TNC is developing a case study in the Coastal Watersheds of Chiapas.  The collection of small basins of the Chiapas Pacific Coast, an area of extremely high biodiversity and cultural significance, were identified by TNC and partners as an ideal region for a pilot test of ELOHA, in addition to other complementary innovative strategies addressing climate change resilience and sustainable financing for watershed protection through water funds.  The CONAGUA has recently initiated the process of calculating within three years, for subsequent publication and regulatory enforcement, the current water availability for all users of the water resources of each of the 24 river basins and their 38 major rivers.  While the NOM-011 does not provide for the inclusion of a volume and associated regime of water flows to maintain river health, in line with the emerging national policy on environmental flows, CONAGUA Chiapas State (division of Water Planning and National System of Information on Water) is willing to include environmental flow allocations within its estimates of future water resources for the basins, if those needs can be estimated by technical experts over a reasonable timeframe.  CONAGUA also intends to support and participate in the development and implementation of environmental flow standards to proactively protect or restore critical freshwater and coastal assets, including within one of their national IWRM flagship project basins located on the Pacific Coast.
At this stage, all available sources of baseline information required for an ELOHA application have been collated and a corresponding metadata inventory compiled. A series of GIS data layers have been prepared, covering the biophysical and select socioeconomic characteristics of the river basins.  All available sources of hydrological data have been identified for the region and a preliminary hydrological classification of river types has been conducted by TNC and the University of Washington.  The next steps include: finalising the river types, after inclusion of a simple fine-scale geomorphic subclassification; working with local ecological experts, including EcoSur, to develop flow-ecology and flow alteration-ecological response relationships for key ecological indicators of river condition, such as fish species and mangrove assemblages; analysing the different basin institutional arrangements across the region, in collaboration with key stakeholders, to be able to set and implement agreed environmental flow standards; developing and setting in motion a monitoring protocol for adaptive flow management; and, not least, incorporating the environmental flow estimates in ongoing basin water availability calculations.
For more information about ELOHA in Mexico, please contact:
Rebecca Tharme
Senior Freshwater Scientist
The Nature Conservancy
Merida, Mexico
Nélida Barajas
Mesoamerican Freshwater Specialist
The Nature Conservancy, Mexico