Reducing the costs of meeting regional water demand through risk-based transfer agreements

Transfers of treated water among inter-connected utilities is becoming more common as the cost of developing new supplies grows, and transfer agreements require well developed rules describing when and how much water will be transferred. The nature of the decision rules governing an agreement must also be coordinated with respect to the treatment and conveyance capacity required to execute the transfers. This study explores different combinations of infrastructure and agreement type that define three different transfer programs, describing the frequency and volume of transfers associated with each, as well as their costs. The agreements are described in terms of the type of decision rule employed: Take-or-Pay, where the timing and quantity of transfers is fixed; Days of Supply Remaining (DSR), which uses a static hydrologic indicator to trigger transfers; and Risk-of-Failure, a probability-based decision rule that involves consideration of both supply and demand. This analysis is conducted within the context of the Research Triangle area of North Carolina (USA), a rapidly growing area that is beginning to approach the practical limits of water resource development. The Risk-of-Failure agreement is shown to reduce the average volume of transfers by over 80% compared to a Take-or-Pay agreement and by roughly half relative to the DSR agreement, leading to significant cost reductions. A utility's willingness to accept something less than guaranteed access to a specified quantity of water (i.e. an interruption) also has a significant impact on cost. Interruptions do not necessarily lead to lower reliability, but rather to the purchasing utility acquiring more water during off-peak periods when the seller has excess treatment capacity available. The lowest cost guaranteed agreement is 40–50% more expensive than the lowest cost interruptible contract.     

From Framework to Action: The DESIRE Approach to Combat Desertification

It has become increasingly clear that desertification can only be tackled through a multi-disciplinary approach that not only involves scientists but also stakeholders. In the DESIRE project such an approach was taken. As a first step, a conceptual framework was developed in which the factors and processes that may lead to land degradation and desertification were described. Many of these factors do not work independently, but can reinforce or weaken one another, and to illustrate these relationships sustainable management and policy feedback loops were included. This conceptual framework can be applied globally, but can also be made site-specific to take into account that each study site has a unique combination of bio-physical, socio-economic and political conditions. Once the conceptual framework was defined, a methodological framework was developed in which the methodological steps taken in the DESIRE approach were listed and their logic and sequence were explained. The last step was to develop a concrete working plan to put the project into action, involving stakeholders throughout the process. This series of steps, in full or in part, offers explicit guidance for other organizations or projects that aim to reduce land degradation and desertification.     

Rewilding in the face of climate change

Expansion of the global protected-area network has been proposed as a strategy to address threats from accelerating climate change and species extinction. A key step in increasing the effectiveness of such expansion is understanding how novel threats to biodiversity from climate change alter concepts such as rewilding, which have underpinned many proposals for large interconnected reserves. We reviewed potential challenges that climate change poses to rewilding and found that the conservation value of large protected areas persists under climate change. Nevertheless, more attention should be given to protection of microrefugia, macrorefugia, complete environmental gradients, and areas that connect current and future suitable climates and to maintaining ecosystem processes and stabilizing feedbacks via conservation strategies that are resilient to uncertainty regarding climate trends. Because a major element of the threat from climate change stems from its novel geographic patterns, we examined, as an example, the implications for climate-adaptation planning of latitudinal, longitudinal (continental to maritime), and elevational gradients in climate-change exposure across the Yellowstone-to-Yukon region, the locus of an iconic conservation proposal initially designed to conserve wide-ranging carnivore species. In addition to a continued emphasis on conserving intact landscapes, restoration of degraded low-elevation areas within the region is needed to capture sites important for landscape-level climate resilience. Extreme climate exposure projected for boreal North America suggests the need for ambitious goals for expansion of the protected-area network there to include refugia created by topography and ecological features, such as peatlands, whose conservation can also reduce emissions from carbon stored in soil. Qualitative understanding of underlying reserve design rules and the geography of climate-change exposure can strengthen the outcomes of inclusive regional planning processes that identify specific sites for protection.     

A BASKET SAMPLING TECHNIQUE FOR QUANTIFYING RIVERINE MACROBENTHOS1

ABSTRACT: A colonization basket sampling technique for quantifying macroinvertebrates in rubble bottom rivers is described. Basket samplers were compared to collections made using the Surber square foot sampler. Procedure for processing samples is described. Macrobenthos were more accurately quantified by basket samplers because both surface and subsurface habitats were sampled, no organisms were lost when samplers were removed from the river, substrata and associated fauna were retained for analysis, and the samplers were used efficiently in both pool and riffle areas. At the end of the colonization period the basket samplers contained one-half cubic foot of river bottom and macroinvertebrates spatially arranged within.     

Nodes,networks, and MUMs: Preserving diversity at all scales

The present focus of practical conservation efforts is limited in scope. This narrowness results in an inability to evaluate and manage phenomena that operate at large spatiotemporal scales. Whereas real ecological phenomena function in a space-time mosaic across a full hierarchy of biological entities and processes, current conservation strategies address a limited spectrum of this complexity. Conservation typically is static (time-limited), concentrates on the habitat content rather than the landscape context of protected areas, evaluates relatively homogeneous communities instead of heterogeneous landscapes, and directs attention to particular species populations and/or the aggregate statistic of species diversity. Insufficient attention has been given to broad ecological patterns and processes and to the conservation of species in natural relative abundance patterns (native diversity).The authors present a conceptual scheme that evaluates not only habitat content within protected areas, but also the landscape context in which each preserve exists. Nodes of concentrated ecological value exist in each landscape at all levels in the biological hierarchy. Integration of these high-quality nodes into a functional network is possible through the establishment of a system of interconnected multiple-use modules (MUMs). The MUM network protects and buffers important ecological entities and phenomena, while encouraging movement of individuals, species, nutrients, energy, and even habitat patches across space and time. An example is presented for the southeastern USA (south Georgia-north Florida), that uses riparian and coastal corridors to interconnect existing protected areas. This scheme will facilitate reintroduction and preservation of wide-ranging species such as the Florida panther, and help reconcile species-level and ecosystem-level conservation approaches.     

Response of Georges Bank cod to periodic and nonperiodic oil spill events

In the management of conflicting dual-resource systems such as continental shelf hydrocarbon extraction and commercial fishing operations, it is necessary to consider the possibility of repeated impact events. The potential magnitude of impacts on Georges Bank fisheries of single oil spill events has been addressed in detail elsewhere (Reed and Spaulding 1979, Reed and others 1980, Spaulding and others 1982). An oil spill-fishery impact estimation model, implemented for the Georges Bank cod fishery (Reed and others 1980), has been used to investigate the potential for nonlinear biological responses to periodic and nonperiodic repetitive spill events. Prerecruit mortality equations incorporating young-of-the-year as well as adult-juvenile interactions, perform acceptably vis-à-vis the historical catch record, but show highly variable behavior under recruitment reductions induced by periodic simulated spills. The results demonstrate the importance of selecting mathematical representations of biological and physical processes underlying population dynamics such that characteristic system behavior is adequately represented in both the time and frequency domains.     

Additional fractionation of sediment oxygen demand

Biological sediment oxygen demand was fractionated into carbonaceous and nitrogenous components. This study, in combination with previous work, provides a procedure for the complete fractionation of sediment oxygen demand for the bottom sediments of lakes and streams. The significance of this study is that this fractionation scheme sheds some lights into the physiological nature of sediments.     

X-ray absorption spectroscopy studies of reactions of technetium, uranium and neptunium with mackinawite

Technetium, uranium and neptunium may all occur in the environment in more than one oxidation state (IV or VII, IV or VI and IV or V respectively). The surface of mackinawite, the first-formed iron sulfide phase in anoxic conditions, can promote redox changes so a series of laboratory experiments were carried out to explore the interactions of Tc, U and Np with this mineral. The products of reaction were characterised using X-ray absorption spectroscopy. Technetium, added as TcO4(-), is reduced to oxidation state IV and forms a TcS(2)-like species. On oxidation of the mackinawite in air to form goethite, Tc remains in oxidation state IV but in an oxide, rather than a sulfide environment. At low concentrations, uranium forms uranyl surface complexes on oxidised regions of the mackinawite surface but at higher concentrations, the uranium promotes surface oxidation and forms a mixed oxidation state oxide phase. Neptunium is reduced to oxidation IV and forms a surface complex with surface sulfide ions. The remainder of the Np coordination sphere is filled with water molecules or hydroxide ions.