Evan Vlachos
Sociology & Civil Engineering
Colorado State University

The use of natural resources and the planning of sustainable water systems are guided by the underlying principle that there should be as little as possible interference with the proper functioning of natural life cycles. Central to such an understanding are also the concepts of “threshold,” and “carrying capacity” as important indicators of ecosystemic balances. Thus, the translation of the above concepts into pertinent indicators (that would also alert policy makers as to the necessary steps for planning and managing sensitive water habitats) requires conceptual clarity, methodological consistency, and well-articulated implementation steps in terms of policy options and intervention strategies.

It is also important to explore how anthropogenic sources of change affect “threshold” considerations, over time and in a cumulative manner. The particular interest here is in addressing the challenge of threshold indicators (and the related “carrying capacity” concept) in terms of cumulative impacts which result from the incremental effects of actions when added to other past, present, and reasonably foreseeable future activities. Such an understanding of threshold criteria can be clarified through such sub-dimensions of cumulative impacts as interactive, diachronic, and synergistic effects and consequences. Measures associated with such multiplicative criteria include among others, tolerance levels, intensity, magnitude, timing, traceability, significance, spatial extent and potential reversibility .

“Thresholds” are, then, part of broader socio-economic considerations for developing more comprehensive policies. In the context of environmental assessment, such complex policies require expanded spatial and time horizons, improved monitoring, innovative institutional mechanisms and new paradigms for defining sustainability criteria. Such comprehensive approaches also require the measuring of significance, the addressing of relative priorities, and the measurement and valuation of the complex sequence of environmental impacts and ecosystemic viability.

The presentation of the material is organized around four major themes of areas of concern:

1. The context of transformation, relating the key concepts of complexity, interdependence and sustainability. Three underlying concerns relate also the forces of volatility, vulnerability, and vigilance accentuating the need for considering extended time and space dimensions.
2. The range of indicators and the questions associated with the search of “thresholds.” The analysis here distinguishes between interesting, important and significant relationships, especially by relating indicators and indices through sustainability matrices. In this context one must also consider the related concepts of carrying capacity, resilience, recuperability, and the underlying concerns with the limits to growth.
3. Complexification and cumulative impacts. By bringing together various shortcomings of present approaches to environmental management, we can outline what Assessment of Cumulative Impacts (ACI) entails. The emerging metaphor of “ecosystem health” can help articulate in a holistic manner the methodological interconnection of cumulative, interactive, and synergistic effects.
4. Theory, modeling and the search for policy guidelines. Using as backdrop the dominant “pressure-response” models (DPSIR) we can better understand the centrality of WFD 2000/60 and the search for Integrated Water Resources Planning and Management. In such an expanding theoretical and methodological context one can also outline environmental unknowns and the utility of scenarios for comprehensive planning and management. A final consideration addresses also capacity building, institutional mobilization, and policy options.

At the end, in order to provide policy guidelines in a fast-changing and complex environment, we must consider what makes a good indicator; the combination of data, information and knowledge; the importance of multiple evaluation criteria; and, the socio-economic context of ecosystem integrity. Thus, an agenda for the future would combine complexity, rapidity of change, uncertainty, and the normative premises of sustainability.