Eco-friendly location of small hydropower

We address the problem of locating small hydropower dams in an environmentally friendly manner. We propose the use of a multi-objective optimization model to maximize total hydropower production, while limiting negative impacts on river connectivity. Critically, we consider the so called “backwater effects” that dams have on power generation at nearby upstream sites via changes in water surface profiles. We further account for the likelihood that migratory fish and other aquatic species can successfully pass hydropower dams and other artificial/natural barriers and how this is influenced by backwater effects. Although naturally represented in nonlinear form, we manage through a series of linearization steps to formulate a mixed integer linear programing model. We illustrate the utility of our proposed framework using a case study from England and Wales. Interestingly, we show that for England and Wales, a region heavily impacted by a large number of existing river barriers, that installation of small hydropower dams fitted with even moderately effective fish passes can, in fact, create a win-win situation that results in increased hydropower and improved river connectivity

A Unified Model for Optimizing Riverscape Conservation

1. Spatial prioritization tools provide a means of finding efficient trade-offs between biodiversity protection and the delivery of ecosystem services. Although a large number of prioritization approaches have been proposed, most are specifically designed for terrestrial systems. When applied to river ecosystems, they often fail to adequately account for the essential role that landscape connectivity plays in maintaining both biodiversity and ecosystem services. This is particularly true of longitudinal connectivity, which in many river catchments is highly altered by the presence of dams, stream-road crossings, and other artificial structures. 2. We propose a novel framework for coordinating river conservation and connectivity restoration. We formulate an optimization model for deciding which subcatchments to designate for ecosystem services and which to include in a river protected area (RPA) network, while also deciding which existing river barriers to remove in order to maximize longitudinal connectivity within the RPA network. In addition to constraints on the size and makeup of the RPA network, the model also considers the suitability of sites for conservation, based on a biological integrity index, and connectivity to multiple habitat types. We demonstrate the usefulness of our approach using a case study involving four managed river catchments located in Hungary. 3. Results show that large increases in connectivity-weighted habitat can be achieved through targeted selection of barrier removals and that the benefits of barrier removal are strongly depend on RPA network size. We find that (i) highly suboptimal solutions are produced if habitat conservation planning and connectivity restoration are done separately and (ii) RPA acquisition provides substantially greater marginal benefits than barrier removal given limited resources. 4. Synthesis and applications. Finding a balance between conservation and ecosystem services provision should give more consideration to connectivity restoration planning, especially in multi-use riverscapes. We present the first modelling framework to directly integrate and optimize river conservation and connectivity restoration planning. This framework can help conservation managers to better account for connectivity, resulting in more effective catchment scale maintenance of biological integrity and ecosystem services delivery

Traffic Modelling at the Port of Dover

The port of Dover has undergone many reincarnations over the centuries: from a fortified port complete with lighthouse in the first century AD, to a military Cinque Port in the middle ages, to the ferry and hovercraft terminal of the late twentieth century. Dover’s principal role now is as a Roll-on, Roll-off (Ro-Ro) Ferry Terminal, in which 2 ferry companies (P&O and DFDS) between them make up to 60 round trips a day to the French Ports of Calais and Dunkerque. They carry over 2.6 million lorries, 2 million cars, and 12 million people a year. The economic value in goods handled through the Port is up to 17% of the UK’s overall trade in goods. Based on 2016 projections, freight traffic is expected to increase by up to 40% in the next 30 years. However, the Dover Eastern Docks Ferry Terminal is small, around half a square kilometre, and expansion is challenging since it is hemmed in by the sea, the White Cliffs of Dover, and Dover town

High value of ecological information for river connectivity restoration

Context: Efficient restoration of longitudinal river connectivity relies on barrier mitigation prioritization tools that incorporate stream network spatial structure to maximize ecological benefits given limited resources. Typically, ecological bene 5 fits of barrier mitigation are measured using proxies such as the amount of accessible riverine habitat. Objectives We developed an optimization approach for barrier mitigation planning which directly incorporates the ecology of managed taxa, and applied it to an urbanizing salmonbearing watershed in Alaska. Methods: A novel river connectivity metric that exploits information on the distribution and movement of managed taxon was embedded into a barrier prioritization framework to identify optimal mitigation actions given limited restoration budgets. The value of ecological information on managed taxa was estimated by comparing costs to achieve restoration targets across alternative barrier prioritization approaches. Results: Barrier mitigation solutions informed by life history information outperformed those using only river connectivity proxies, demonstrating high value of ecological information for watershed restoration. In our study area, information on salmon ecology was typically valued at 0.8-1.2M USD in costs savings to achieve a given benefit level relative to solutions derived only from stream network information, equating to 16-28% of the restoration budget. Conclusions Investing in ecological studies may achieve win-win outcomes of improved understanding of aquatic ecology and greater watershed restoration efficiency

Summary and key findings from Big Lake barrier prioritization analysis – A report to USFWS, Anchorage Field Office

A state-of-the-art optimization model was developed for prioritizing investments in culvert mitigation actions within the Big Lake area of Alaska. Unlike existing prioritization models, the model takes into account the spatial distribution of key habitats required throughout the full coho salmon life-cycle, the dispersal capabilities of fish, and the upstream/downstream passability of barriers. The model represents a radical improvement over the variety of ad-hoc methods commonly used in barrier prioritization planning (i.e., scoring and ranking procedure) and even existing optimization approaches aimed at improving connectivity for migratory fish. At present, just under half of river habitat in the Big Lake basin is currently available for meeting the life-cycle needs of coho. Access to winter rearing habitat (from age 0 summer rearing areas) limits connectivity the most (30% reduction in connectivity), followed by spawning grounds (17% reduction) and age 1+ summer rearing (15% reduction). Age 0 summer rearing and outward smolt migration do not have any substantial impact on connectivity. To increase available habitat to 100% would require the removal of 29 out of 60 existing culverts in the Big Lake basin at an estimated cost of approximately $6.8M. A 50$3M. Certain high-frequency culverts (those selected a high proportion of time by the optimization model) have lower than average passability for juveniles and adults, very large amounts upstream spawning, summer (for age 0 and 1+ juveniles), and winter rearing habitat, and significantly higher than average mitigation costs compared to culverts as a whole. These are mostly located near key strategic lakes or on mainstem stretch of river, which form major thoroughfares for coho dispersal

ResFish v1.0 user manual

ResFish v1.0 is a program written in Java for planning the repair and removal of artificial in-stream barriers, which impair regular seasonal movements of resident fish species and other freshwater aquatic biota. The program uses a state-of-the-art heuristic solution algorithm (described below) to select barriers for repair or removal in order to maximize the connectivity of stream reaches within a watershed, subject to a limited budget on the total cost of barrier removal and repair actions. More specifically, the program maximizes overall connectivity weighted habitat based on the Cind connectivity metric (Deibel et al. 2009), which accounts for the amount (length), quality and distance of different habitat types (e.g., stream orders) that can be accessed by stream-resident fish from any given focal stream segment by successfully traversing upstream/downstream and back again through any intervening artificial or natural barriers. More specific details on the structure and formulation of the ResFish decision problem are given the Appendix below. Access to a range of different habitat (steam orders) types is important not only as part of the normal life-cycle of resident fish (e.g., movement from spring spawning areas in low order headwaters to summer feeding grounds in mid-order streams to over-wintering areas in deep water pools) but also provides access to refugia during large disturbances, such as floods and droughts, and has been shown to be an important determinant of stream-level species richness (Deibel et al. 2009). The primary output of ResFish consists of an optimal to near optimal list of barrier removal/repair actions, the corresponding level of habitat connectivity and the total cost of barrier repair and removal

OptiPass: The migratory fish passage optimization tool, version 1.0 user manual

OptiPass(TM) is a Microsoft Windows® based program for optimizing the mitigation of artificial barriers, which block or otherwise reduce the dispersal of diadromous (aka migratory) fish. The program integrates information on barrier passability (upstream and or downstream), mitigation cost, and potential river habitat gain for one or more target species in order to identify cost-efficient passage improvement strategies. Critically, OptiPass employs state-of-the-art optimization modeling and solution techniques, explicitly taking into consideration the spatial structure of barriers and the interactive effects of passage improvement on longitudinal connectivity. Optimization based methods provide a systematic and objective means of targeting barrier mitigation actions which maximize restoration gains given available resources. OptiPass represents a radical improvement over the ad-hoc methods commonly used in barrier prioritization planning. OptiPass comes replete with a graphical user interface to quickly and easily generate optimized solutions. Additional functionalities have been built into OptiPass for performing batch runs across a range of budget values, varying the weights placed on different target species, and carrying out more detailed “what-if” type analyses such as changing the spatial focus (i.e., selecting subsets of watersheds for detailed study) and forcing specific barriers in or out of the final optimal solution. Besides being useful for strategically targeting high impact barriers within a given area that yield the “biggest bang for the buck,” OptiPass can also be used in a variety of other ways such as in the short-listing of projects submitted for potential funding and helping to identify appropriate levels of investment in barrier mitigation that meet defined policy planning goals

Open rivers: Barrier removal planning and the restoration of free-flowing rivers

Restoration of unobstructed, free-flowing sections of river can provide considerable environmental and ecological benefits. It removes impediments to aquatic species dispersal and improves flow, sediment and nutrient transport. This, in turn, can serve to improve environmental quality and abundance of native species, not only within the river channel itself, but also within adjacent riparian, floodplain and coastal areas. In support of this effort, a generic optimization model is presented in this paper for prioritizing the removal of problematic structures, which adversely affect aquatic species dispersal and river hydrology. Its purpose is to maximize, subject to a budget, the size of the single largest section of connected river unimpeded by artificial flow and dispersal barriers. The model is designed to improve, in a holistic way, the connectivity and environmental status of a river network. Furthermore, unlike most previous prioritization methods, it is particularly well suited to meet the needs of potamodromous fish species and other resident aquatic organisms, which regularly disperse among different parts of a river network. After presenting an initial mixed integer linear programming formulation of the model, more scalable reformulation and solution techniques are investigated for solving large, realistic-sized instances. Results from a case-study of the Pike River Watershed, located in northeast Wisconsin, USA, demonstrate the computational efficiency of the proposed model as well as highlight some general insights about systematic barrier removal planning