A robust conceptual framework is necessary to provide the foundation for development of a consistent and systematic set of indicators to measure the sustainability of freshwater systems (OECD 2008). A conceptual framework is an abstract representation of complex freshwater systems that simplifies and highlights the components and relationships between the social and ecological systems. A conceptual framework characterizes the multi-faceted and complex nature of these systems. And by capturing generalities is relevant across a wide range of systems, scales and time periods (Shields and Rangarjan 2013). Hence, the conceptual framework should clearly describe and define relevant multi-dimensional phenomenon, structure how the components are connected and nested; highlight how components relate to freshwater health; and guide indicator selection (OECD 2008).
We invoke the concept of a freshwater social-ecological system to illustrate the different dimensions that need to be measured to understand how social, hydrologic and ecological systems interact (Vogel et al., 2015; Vollmer et al., 2016). Many conceptual models have been developed for freshwater systems (Binder et al. 2013), however most do not account for the feedback between the ecosystems that capture, store and deliver water-based services; the beneficiaries of those services; and how freshwater systems are governed and managed (Vollmer et al., 2016). We adapted Ostrom's (2009) framework for analyzing social-ecological system sustainability to freshwater systems. Ostrom's (2009) framework is suitable for systems with strong feedbacks between ecosystems, the services they provide and the beneficiaries of those services; as it treats the social and ecological components in almost equal depth and highlights their interactions (Binder et al. 2013). Our conceptual framework here consists of three main components: "Ecosystem Vitality," "Ecosystem Services" and "Governance & Stakeholders." (Figure 1).
Figure 1. Conceptual framework for freshwater social-ecological systems comprised of Ecosystem Vitality, Ecosystem Services, and Governance & Stakeholders. Stakeholders set and adapt rules within governance and market systems and also respond to them. Within the constraints and rules set by water governance, stakeholders modify ecosystems through land-use change or conservation to exploit or manage freshwater ecosystems, and by developing infrastructure and technology to access water-based ecosystem services. Modifications to ecosystems and water withdrawals can alter the flow regime and water quality and thereby affect delivery of ecosystem services to beneficiaries. In basins where there are competing water needs, trade-offs become apparent and may necessitate an adjustment to governance mechanisms that can trigger changes in markets. Freshwater SESs are also impacted by external biophysical influences such as drought or climate change that affect ecosystem service delivery that can feed back to affect governance. Basins also are embedded within a broader social, political and economic context that can influence governance systems and fresh water management. While we recognize that water and water-based goods and services may also be imported into or exported from a basin, our focus is primarily on interactions within the basin.
"Ecosystem Vitality" refers to the long-term maintenance of "ecosystem structure and processes that underpin the capacity of an ecosystem to provide [water-based] goods and services" (MEA 2005, Turkelboom et al. 2014). Freshwater ecosystems include aquatic as well as terrestrial ecosystems linked within a watershed, encompassing both surface and groundwater.
Ecosystems produce a range of benefits to stakeholders ("Ecosystem Services") such as water provision, hazard mitigation and cultural services such as recreation opportunities (Haines-Young and Potschin 2010; 2013). Stakeholders operating within a governance system modify and manage the ecosystem to obtain certain services. Modifications might include channel and flow manipulations, pollution and remediation activities, as well as changes to the terrestrial ecosystem that impact on water-related services, such as land-use change that accelerates runoff downstream or habitat restoration. Hence, the structure and function of the ecosystem affects, and is affected by, the delivery of ecosystem services. Stakeholders operating within a governance system also build hard infrastructure to improve the delivery of ecosystem services or compensate for losses of naturally-provided services. These modifications to, and withdrawals from, the freshwater system can involve trade-offs among different objectives, different ecosystem services, beneficiary groups and generations (RodrÃguez et al., 2006, Cai et al., 2002).
"Governance & Stakeholders" is defined as "the structures and processes by which people in societies make decisions and share power, creating the conditions for ordered rule and collective action, or institutions of social coordination" (Schultz et al. 2015). This definition encompasses multiple tiers of government, their formal rules and informal norms (e.g., community-established guidelines) and market mechanisms. It also encompasses a range of stakeholders comprising decision makers and the human beneficiary population (from individual citizens and community groups to municipalities, corporations and international organizations), as well as other stakeholders such as donor agencies, who may not directly benefit from the ecosystem services in a particular location, but nonetheless have an interest in, and influence over, decisions that affect a particular basin. The geographic range and makeup of stakeholders also changes according to the ecosystem service, e.g., beneficiaries of water-related recreation may live far outside of the basin generating the service. Stakeholders operate within the constraints of the governance system, which affects the behavior of stakeholders. In turn, stakeholders may influence or shape the governance system by modifying rules or changing the makeup of the system. While stakeholders and governance systems can be regarded as separate entities, we combine them into a single set of indicators because of the heavy reliance of each on the other, and the tight feedback that connects them.
Various forms of governance collectively provide the constraints and opportunities within which decisions are made, and then shape the consequences of these decisions (McGinnis, 2011). Here, we distinguish between governance systems directly related to water versus the broader social, economic or political context in which water governance lies. All variables (and their indicators) for the relevant governance system should be directly related to water, and these variables should be under the direct influence of at least some of the stakeholders. While general indicators, such as political stability, may provide context and may indirectly influence water governance, they are not sufficiently specific to be tracked as a characteristic of a river basin's governance system.
Additionally, the freshwater system is affected by external biophysical stressors, e.g. climate change, drought and floods, as well as social, economic and political contexts, which operate at a scale larger than the watershed. Water or water-dependent products can be imported or exported to beneficiaries within and outside of the watershed. These aspects provide additional context for evaluating, monitoring and managing freshwater systems while not explicitly influencing indicator selection. This social-ecological conceptual framework is considered the most appropriate for characterizing freshwater health because it provides an integrative conceptualization of the complex dynamics in social-ecological problems relating to sustainability. Its underpinnings are based on theories of collective choice, common-pool resources and natural resource management; and the ecological and social systems are treated in equal depth (Ostrom 2009; Binder et al. 2013). The social system (i.e., governance and stakeholders) operates at both the micro and macro level in a feedback loop: The micro level includes individual decision making whereas the macro level depicts the social system at the level of a population or society. Furthermore, the conceptual framework explicitly depicts the reciprocity, or feedback, between the social and ecological systems through specified interactions. It can be applied to multiple spatial scales (McGinnis and Ostrom, 2014), including watersheds and nations as well as the global freshwater system (Vogel et al., 2015).
The conceptual framework formed the basis of the development of the Freshwater Health Index indicators. Selection criteria are typically used to ensure that indicators are relevant and meet the purpose of the conceptual framework. Numerous criteria have been proposed for a variety of indicator frameworks (e.g. Smith and Zhang 2004; SWRR 2005; OECD 2008), and these were used to develop and refine our criteria for indicator selection to measure freshwater health. We applied the following criteria to ensure relevance, accessibility and soundness of our freshwater health indicators:
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indicators must be measurable, unbiased and defensible,
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choice of indicators must be relevant and guided by the conceptual framework,
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indicators must be relatively easy to understand,
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indicators must be based on information that can be used to compare different geographical areas and contexts,
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indicators must be distinct, i.e., an indicator does not measure the same process or quantity as another indicator,
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indicators or their combinations should be limited in number to provide a clearer signal of progress,
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indicators must be sensitive to changes over time and space to detect change.