Millennial‐Length Records of Streamflow From Three Major Upper Colorado River Tributaries1

Gray, Stephen T., Jeffrey J. Lukas, and Connie A. Woodhouse, 2011. Millennial‐Length Records of Streamflow From Three Major Upper Colorado River Tributaries. Journal of the American Water Resources Association (JAWRA) 47(4):702‐712. DOI: 10.1111/j.1752‐1688.2011.00535.x Abstract: Drought, climate change, and shifting consumptive use are prompting a widespread reassessment of water availability in the Upper Colorado River basin. Here, we present millennial‐length records of water year (October‐September) streamflow for key Upper Colorado tributaries: the White, Yampa, and Little Snake Rivers. Based on tree rings, these records represent the first paleohydrological reconstructions from these subbasins to overlap with a series of Medieval droughts (∼ad 800 to 1300). The reconstructions show marked interannual variability imbedded in nonstationary behavior over decadal to multidecadal time scales. These reconstructions suggest that, even in a millennial context, gaged flows from a handful of years (e.g., 1977 and 2002) were extremely dry. However, droughts of much greater duration and magnitude than any in the instrumental record were regular features prior to 1900. Likewise these reconstructions point to the unusual wetness of the gage period, and the potential for recent observations to paint an overly optimistic picture of regional water supplies. The future of the Upper Colorado River will be determined by a combination of inherent hydroclimatic variability and a broad range of human‐induced changes. It is then essential that regional water managers, water users, and policy makers alike consider a broader range of hydroclimatic scenarios than is offered by the gage record alone.     

The cost-effectiveness of residential radon remediation programmes: assumptions about benefits stream profiles over time

A recent cost-effectiveness analysis of a residential radon remediation programme considered and highlighted many areas of uncertainty in the parameters chosen for the analysis. One assumption not challenged in the study was the benefits stream profile adopted. There are several different ways of loading the benefits in terms of life years into the cost-effectiveness model and several of these are explored and the results are reported in this study. The benefits profile depends upon the lead-time to cancer manifestation post environmental carcinogen (radon) exposure. The literature reviewed suggests that there are many options for loading benefits to radon-induced lung cancer prevention programmes. In this study, the alternative benefits stream profiles are explored and their implications for the cost-effectiveness ratio are examined. Adopting different benefits stream profiles to the model results in a range of cost-effectiveness ratios from 14912.90 pounds per life year gained to 52416.27 pounds per life year gained. The preferred model is reported where the life years gained are assumed to be equally distributed over the last 15 years of the 40-year time horizon of the analysis (Y25-40) and the corresponding cost-effectiveness ratio is 37,943 pounds per life year gained.     

Stable macrofauna community structure despite fluctuating food supply in subtidal soft sediments of Oslofjord,Norway

At a locality at 32-m depth in Oslofjord, Norway, temperature varied from 4.8° to 9.2°C and salinity varied from 31.2 to 33.3 S over a two-year period. There was a peak in chlorophyll a, and C and N in April–June and a smaller peak in November in the sediment. Bacterial numbers showed maxima in July–August and November–December. The macrobenthic fauna was typical of a species-rich and undisturbed boreal community of silt-clay sediments. The community was predominantly composed of surface and subsurface deposit feeders. Over the twoyear period there was little variation in numerical abundance or biomass of the species despite the variation in food input. The lack of seasonality shown by the fauna probably relates to the lack of variability of the physical environment. The mechanism by which this control is achieved, however, is not known. There are large predators/disturbers in the community such as the polychaetes Lumbrineris fragilis, Glycera rouxii, G. alba, Nephthys spp. and the echinoid Brissopsis lyrifera, which probably play an important role in structuring the community.     

Leaf litter breakdown in streams receiving treated and untreated metal mine drainage

Rates of alder leaf decomposition were used as an ecosystem-level measure of effects of untreated and treated acid mine drainage on two Colorado mountain streams. Untreated mine effluents had low pH and high concentrations of metals, particularly iron. Deposition of ferric hydroxide on leaf surfaces inhibited colonization by decomposers, such as fungi and aquatic insects, and thus little leaf breakdown occurred. Treated effluents had improved water quality (basic pH, low metal concentrations), but suspended flocs released by the treatment process buried leaves and reduced consumer activity. The rate of leaf breakdown was not significantly different from the rate with untreated effluents; thus improvement in water quality alone was insufficient to restore this important pathway of energy flow in headwater streams.