Hundreds of methods exist for defining environmental flows. Those seeking to conduct environmental flow assessments often seek guidance on which method is “best.” Here we avoid a simple answer to that question and instead describe a flexible and iterative framework that intertwines environmental flow assessment with environmental flow implementation. This Three-Level Framework is designed so that environmental flow practitioners identify the “best” method — or more likely, methods — based on the amount of resources and data available, the most important issues and uncertainties and the level of certainty required. The framework emphasizes the strategic deployment of resources to an integrated program of environmental flow assessment, development and implementation of flow prescriptions and adaptive management.
Below are links to descriptions of the three levels. The Conservancy has developed or contributed to a number of tools or approaches that fit within this Three-Level Framework. These have their own resource pages and are listed under the corresponding level below.
Three-Level Framework Overview
Level 1: Comprehensive hydrologic desktop methods
Level 2: Expert Panel Assessment
Level 3: Examining Tradeoffs and Predicting Results of Operational Changes
Software:
- Indicators of Hydrologic Alteration (IHA) is a free software program developed by Conservancy scientists, which provides useful information for developing environmental flow recommendations and understanding the impacts of human activities on water flows. Using daily water flow or level data as input, IHA calculates 67 ecologically relevant hydrologic statistics, including environmental flow components. IHA can display statistical information about water flow changes and trends in multiple formats, such as comparing the water flow in a particular river between pre-dam and post-dam periods. The IHA website offers free software, tutorials, users manuals, related literature, project database, and an active user discussion group.
- U.S. Army Corps of Engineers Hydraulic Engineering Center (HEC) modeling software supports environmental flow assessment and implementation:
Books:
Rivers for Life
Leading water experts Sandra Postel and Brian Richter explain why restoring and preserving more natural river flows are key to sustaining freshwater biodiversity and healthy river systems, and describe innovative policies, scientific approaches and management reforms for achieving those goals.
Practitioner's Guide to Freshwater Biodiversity Conservation
Conserving freshwater biodiversity presents unique challenges for conservation practitioners. Meeting these challenges requires understanding how freshwater ecosystems are formed and how they function. It requires identifying the best strategies to pursue in the face of existing threats to freshwater ecosystems and identified conservation targets.
Managing Freshwater Inflows to Estuaries - A Methods Guide
The management of freshwater and the management of estuaries have in most countries evolved as independent programs that operate with distinct mandates, authorities, policies and institutional structures. This guide addresses the need to better integrate river and catchment (watershed) management with estuary management by combining important features of integrated coastal management (ICM) with integrated water resources management (IWRM). The Methods Guide is published by USAID, The Nature Conservancy and The Coastal Resource Center at The University of Rhode Island.
