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We developed an integrated hydrologic model of the upper Nushagak and Kvichak watersheds in the Bristol Bay region of southwestern Alaska, a region under substantial development pressure from large-scale copper mining. We incorporated climate change scenarios into this model to evaluate how hydrologic regimes and stream temperatures might change in a future climate, and to summarize indicators of hydrologic alteration that are relevant to salmon habitat ecology and life history. Model simulations project substantial changes in mean winter flow, peak flow dates, and water temperature by 2100. In particular, we find that annual hydrographs will no longer be dominated by a single spring thaw event, but will instead be characterized by numerous high flow events throughout the winter. Stream temperatures increase in all future scenarios, although these temperature increases are moderated relative to air temperatures by cool baseflow inputs during the summer months. Projected changes to flow and stream temperature could influence salmon through alterations in the suitability of spawning gravels, changes in the duration of incubation, increased growth during juvenile stages, and increased exposure to chronic and acute temperature stress. These climate-modulated changes represent a shifting baseline in salmon habitat quality and quantity in the future, and an important consideration to adequately assess the types and magnitude of risks associated with proposed large-scale mining in the region.

The Pebble Project in Alaska is one of the world’s largest undeveloped copper deposits. The Environmental Impact Statement (EIS) proposes a 20-year open-pit extraction, sulfide flotation, and deposition of separated pyritic tailings and potentially acid-generating waste rock in the pit at closure. The pit will require perpetual pump and treat management. We conducted geochemical and integrated groundwater–surface water modeling and streamflow mixing calculations to examine alternative conceptual models and future mine abandonment leading to failure of the water management scheme 100 years after mine closure. Using EIS source water chemistry and volumes and assuming a well-mixed pit lake, PHREEQC modeling predicts an acidic (pH 3.5) pit lake with elevated copper concentrations (130 mg/L) under post-closure conditions. The results are similar to water quality in the Berkeley Pit in Montana, USA, another porphyry copper deposit pit lake in rocks with low neutralization potential. Integrated groundwater–surface water modeling using MIKE SHE examined the effects of the failure mode for the proposed 20-year and reasonably foreseeable 78-year expansion. Simulations predict that if pumping fails, the 20-year pit lake will irreversibly overtop within 3 to 4 years and mix with the South Fork Koktuli River, which contains salmon spawning and rearing habitat. The 78-year pit lake overtops more rapidly, within 1 year, and discharges into Upper Talarik Creek. Mixing calculations for the 20-year pit show that this spillover would lead to exceedances of Alaska’s copper surface water criteria in the river by a factor of 500–1000 times at 35 miles downstream. The combined modeling efforts show the importance of examining long-term failure modes, especially in areas with high potential impacts to stream ecological services.

We developed an integrated hydrologic model of the upper Nushagak and Kvichak watersheds in the Bristol Bay region of southwestern Alaska, a region under substantial development pressure from large-scale copper mining. We incorporated climate change scenarios into this model to evaluate how hydrologic regimes and stream temperatures might change in a future climate, and to summarize indicators of hydrologic alteration that are relevant to salmon habitat ecology and life history. Model simulations project substantial changes in mean winter flow, peak flow dates, and water temperature by 2100. In particular, we find that annual hydrographs will no longer be dominated by a single spring thaw event, but will instead be characterized by numerous high flow events throughout the winter. Stream temperatures increase in all future scenarios, although these temperature increases are moderated relative to air temperatures by cool baseflow inputs during the summer months. Projected changes to flow and stream temperature could influence salmon through alterations in the suitability of spawning gravels, changes in the duration of incubation, increased growth during juvenile stages, and increased exposure to chronic and acute temperature stress. These climate-modulated changes represent a shifting baseline in salmon habitat quality and quantity in the future, and an important consideration to adequately assess the types and magnitude of risks associated with proposed large-scale mining in the region.

A conceptual and modeling framework to study groundwater recharge in arid/semi-arid flow systems is developed using a fully-integrated, physically-based, hydrologic code and GIS techniques. The framework is constructed by modeling recharge in a well-studied, large basin flow system (>20,000 km2), located in northeastern Arizona, using available unsaturated zone and integrated hydrologic flow codes and then conducting a sensitivity analysis. Eleven different mechanisms that describe recharge within the basin are identified and defined in this study as hydrogeomorphic units (HGU). The relative importance and dynamics of recharge in each of these HGUs is assessed using several years of high-resolution temporal climate input. Next, a fully integrated basin flow model is developed using 75 years of daily climate data (1920 to 1995) from NWS stations. Daily climate data are disaggregated to hourly distributions using available higher temporal resolution data to evaluate the spatial distribution of basin recharge. Initial simulations proved computationally inefficient and output was difficult to interpret. An important step in the proposed framework involves systematically developing increasingly complex sub-regional scale and partially-coupled flow process models to better understand the sensitivity of recharge to individual processes and parameters. Results of these sensitivity analyses indicate that good spatial distributions of saturated hydraulic conductivity and high temporal resolution of precipitation and potential evapotranspiration are essential for estimating realistic basin recharge rates. Predicted basin recharge rates (30 to 120 mm/year) vary spatially and temporally, but are similar to other reported rates for large semi-arid/arid basins (3.5 to 26.6% of annual precipitation). Simulated flows in HGUs, however, suggest that recharge in coarser regional integrated model grid cells is likely under-predicted where significant concentrated surface runoff, or ponding occurs. Results also suggest that traditional, empirical recharge methodology (like Maxey-Eakin) do not consider important parameters and can yield poor spatial and temporal basin recharge estimates. Integrated hydrologic models offer tremendous potential in studying complex, integrated hydrologic conditions in arid/semi-arid systems, so that fundamental basin-scale mechanisms and processes that govern recharge can be better understood. However, several limitations were identified and must be considered in their development and application.

The productivity slowdown of the 1970s and 1980s and the resumption of productivity growth in the 1990s have provoked controversy among policymakers and researchers. Economists have been forced to reexamine fundamental questions of measurement technique. Some researchers argue that econometric approaches to productivity measurement usefully address shortcomings of the dominant index number techniques while others maintain that current productivity statistics underreport damage to the environment. In this book, the contributors propose innovative approaches to these issues. The result is a stat

Automotive castings are being utilized increasingly in structurally demanding and safety critical applications. The need for reduced weight, near net shape and more cost effective components has resulted in a desire by the customer to reduce the conservative safety factors previously used for design criteria. The expectation on the metal caster is to supply parts with material and structural properties verified in the product to a high statistical standard. Since the part's quality and integrity are now guaranteed, the historical approach of manual inspection, evaluation and qualitatively based acceptance decisions is being replaced with various approaches to automated evaluation. This presentation will review some of the past requirements and testing approaches used to assure part integrity and compliance. Then it will look at the work of groups like the RISC committee of USAMP/USCAR to make standards more quantitative. This discussion sets the background for introducing PCRI, an NDE (Non Destructive Evaluation) method that evaluates parts not in terms of specific indications, but rather in terms of their structural properties, which better determine fitness for use. [Example material: A206].

Automotive castings are being utilized increasingly in structurally demanding and safety critical applications. The need for reduced weight, near net shape and more cost effective components has resulted in a desire by the customer to reduce the conservative safety factors previously used for design criteria. The expectation on the metal caster is to supply parts with material and structural properties verified in the product to a high statistical standard. Since the part's quality and integrity are now guaranteed, the historical approach of manual inspection, evaluation and qualitatively based acceptance decisions is being replaced with various approaches to automated evaluation. This presentation will review some of the past requirements and testing approaches used to assure part integrity and compliance. Then it will look at the work of groups like the RISC committee of USAMP/USCAR to make standards more quantitative. This discussion sets the background for introducing PCRI, an NDE (Non Destructive Evaluation) method that evaluates parts not in terms of specific indications, but rather in terms of their structural properties, which better determine fitness for use.