**Preface to "A Systems Approach for River and River Basin Restoration"**

This book investigates new approaches to river basin restoration as well as the most effective leverage points for achieving meaningful change and expectations in the behavior of those river basins. River and river basin restoration faces significant technical challenges as well as challenges to our conception or paradigm for the purpose of the river basin. This article defines the term restoration as reestablishing the structure and function of an ecosystem, yet invites readers to substitute in the terms rehabilitation, defined as making an ecosystem useful after disturbance, or reclamation, defined as changing the biophysical capacity of an ecosystem. The major technical challenges include the following: (a) the restoration target is often unknown, is not likely an initial or completely natural state, and remains poorly understood; (b) restoration structures should provide multiple functions across seasonal flow regime to benefit humans and biodiversity; (c) restoration spatial scale and complexity should consider local to basin-level issues; (d) restoration resiliency should handle uncertain future drivers related to urbanization and climatic disruption.

Human systems and ecosystems are separated to show their interaction in the United Nations model of the river basin system, recognizing the agency of humans to affect change, i.e., the Anthropocene epoch. In this model, humans depend on services from the same ecosystems we diminish by polluting, harvesting, and other pressures (e.g., climate disruption). Furthermore, humans can assess the actual state of the ecosystem (e.g., water volume or quality) and compare it with our desires for the state of the ecosystem (e.g., below target) For our river basin restoration, which may be active or passive, we used a comparison of the actual and desired state of the system to formulate the paradigm rather than the policy which is a novel addition to this model. This book will demonstrate that the task of formulating our paradigm for the purpose of a river basin is equally if not more important than the list of major technical challenges for river basin restoration.

River basin scientists and engineers have made important progress in recognizing that these challenges are all part of a single complex system, noting that tinkering with elements in one location or time tends to impact the state or function of elements in other parts of the system. Managing the complexity of the river basin system is yet another challenge and progress in this area requires a better understanding of systems and their leverage points.

This book provides new insights on how to strategically use leverage points to restore river basin systems. The most effective leverage point is transcending paradigms and developing new mindsets for working with the complexity of river basin systems. Of course, developing the paradigm is part of the system. So the systems path that scientists and engineers might follow in restoration, as adapted from the UN, is as follows: (1) identifying, understanding, and working with the physical, chemical, and biological processes comprising river basin and river health and delivering ecosystem services; (2) identifying, incorporating, and involving socio-economic values and broader planning and development activities linked to river basin and river health; (3) addressing structure and function relationships at the appropriate scales to address limiting factors to river health; (4) setting clear, achievable, and measurable goals, framed in terms of changes to ecosystem structure and function, the provisioning of ecosystem services, and, where feasible, socioeconomic factors; (5) planning, implementing, and managing to provide resilience to a range of scenarios over time, including changes to climate, land use, hydrology, pollutant loads, and population, so restoration outcomes are sustained over the long term; (6) involving all relevant stakeholders in an integrated approach, addressing land and water issues, and involving interagency and community collaboration, to achieve the greatest benefits; and (7) monitoring, evaluating, adapting, and reporting the actual state of river basin health relative to the desired state, and formulating our paradigm to guide restoration and adaptive management. Together on this journey, we can improve social and ecological systems within our river basins.

> **Theodore Endreny** *Editor*
