The potential for agricultural land use change to reduce flood risk in a large watershed

Effects of agricultural land management practices on surface runoff are evident at local scales, but evidence for watershed‐scale impacts is limited. In this study, we used the Soil and Water Assessment Tool model to assess changes in downstream flood risks under different land uses for the large, intensely agricultural, Raccoon River watershed in Iowa. We first developed a baseline model for flood risk based on current land use and typical weather patterns and then simulated the effects of varying levels of increased perennials on the landscape under the same weather patterns. Results suggest that land use changes in the Raccoon River could reduce the likelihood of flood events, decreasing both the number of flood events and the frequency of severe floods. The duration of flood events were not substantially affected by land use change in our assessment. The greatest flood risk reduction was associated with converting all cropland to perennial vegetation, but we found that converting half of the land to perennial vegetation or extended rotations (and leaving the remaining area in cropland) could also have major effects on reducing downstream flooding potential. We discuss the potential costs of adopting the land use change in the watershed to illustrate the scale of subsidies required to induce large‐scale conversion to perennially based systems needed for flood risk reduction. Copyright © 2013 John Wiley & Sons, Ltd.     

APPARENT THERMAL DIFFUSIVITY IN SOIL: ESTIMATION FROM THERMAL RECORDS AND SUGGESTIONS FOR NUMERICAL MODELING

The concept of apparent thermal diffusivity in soil is discussed and defined as consisting of an intrinsic and a pseudo part. A method that uses a numerical model of heat conduction and measured soil temperatures to estimate apparent thermal diffusivity is introduced. The method requires measurement of temperatures at three depths to make an estimate for diffusivity between the lowest and uppermost depths. This method is applied to a five-day data set obtained in Sweden. Time-dependent apparent diffusivities are estimated for periods of five days, one day, and three hours. An empirical method is used to determine the intrinsic diffusivity. Values close to those calculated for the empirical relationships have been obtained for the one- and five-day periods, whereas values of the three-hour period show wider variation. The results indicate that the outlined method is feasible and satisfactory for estimating the intrinsic thermal diffusivity in soils near the surface on a daily basis. It also is argued that the root-mean-square error (RMSE) of a simulation using the estimated diffusivity, together with the diffusivity, is a better indicator for non-conductive processes than diffusivity alone.     

A summary of past and recent plankton of Lake Winnipeg, Canada using algal fossil remains

Although the phytoplankton and protozoan assemblages of Lake Winnipeg are quite variable both, spatial and temporally, knowledge of their current distribution and ecology enables them to be used as indicators providing unique information concerning past and recent ecosystem conditions. Many of the main taxa have been similar throughout history although there have been dramatic changes in their abundance. Lake Winnipeg is currently very responsive to the climatic conditions in its drainage basin and it appears, historically, to have been a diatom-bluegreen algal lake with Tintinnids and thecate amoeba forming significant components of the protozoan community. A wide variety of microfossil remains have been used to infer past conditions in this large prairie lake. Microfossils reported from the long core 103 (8 m) taken from the north basin of LakeWinnipeg and short core Namao 7a taken from the south basin of the lake in August 1994 indicate that the lake has experienced several changes over its history. Diatom assemblages, low throughout the core 103 below 50 cm, except for a peak around 300–400 cm are virtually absent below 690–800 cm (Lake Agassiz). Stephanodiscus and Aulacoseira are the two major pelagic diatom genera represented throughout the lake's history. Species changes occur near the top of the core indicate increased anthropogenic eutrophication. Shallow water littoral taxa were never abundant at either coring sites. The presence of planktic cyanoprokaryote (cyanophyte, cyanobacteria, bluegreen algae) remains (akinetes) from 600 cm depth and the progressive increase in abundance from 400 cm to through the top 100 cm of the core indicates increasing phosphorus levels, warming summer temperatures and increasing summer nitrogen limitation in the lake. Nitrogen fixing bluegreens (especially Anabaena and Aphanizomenon akinetes) and the diatoms (Aulacoseira ambigua, A. granulata, A. islandica, S. binderanus, and S. niagarae) were abundant in the upper sediments and changes after 100 cm can be interpreted as the effects of human impact. These taxa indicative of increase eutrophication, in addition to S. agassizensis, Melosira varians and Cyclostephanos dubius, are representative of present day plankton. The short core Namao 7a was dated by ^Pb210 and the fossil remains also show a rise in the Aulacoseira (particularly A. granulata and A. ambigua) and bluegreen akinetes in the last 40 years as was seen in the upper sediments of the 103 core. There was an interesting peak in chrysophyte cysts during the 1930's which corresponds nicely with climatic conditions during this period. The fires accompaning the hot dry period in the mid 70's can be seen in the dramatic rise in charcoal during this period. Multiple types of micro fossils remains provides several useful tools for interpreting past lacustrine conditions.     

Variability of in‐stream and riparian storage in a beaded arctic stream

The extent and variability of water storage and residence times throughout the open water season in beaded arctic streams are poorly understood. Data collected in Imnavait Creek, a beaded stream located north of the Brooks Range in Alaska, were used to better understand the effects of in‐pool and riparian storage on heat and mass movement through beaded streams. Temperature data of high spatial resolution within the pools and surrounding sediments were used with volumetric discharge and electrical conductivity to identify storage areas within the pools, banks, and other marshy areas within the riparian zone, including subsurface flow paths that connect the pools. These subsurface flows were found to alter water conductivity and the character of dissolved organic matter (DOM) in short reaches (10 s of m) while influencing the chemistry of downstream pools. During low flow periods, persistent stratification occurred within the pools due to absorption of solar radiation by DOM coupled with permafrost below and low wind stress at the pool surface. Additionally, one of the shallow pools (<0.5 m depth) remained stratified during higher flow periods and lower radiation inputs due to dense subsurface flows entering the bottom of the pools. This consistent separation of surface and bottom water masses in each pool will increase the travel times through this and similar arctic watersheds, and therefore will affect the evolution of water chemistry and material export. Copyright © 2011 John Wiley & Sons, Ltd.     

Performance of the COSERO precipitation–runoff model under non-stationary conditions in basins with different climates

Abstract

This study is a contribution to a model intercomparison experiment initiated during a workshop at the 2013 IAHS conference in Göteborg, Sweden. We present discharge simulations with the conceptual precipitation–runoff model COSERO in 11 basins located under different climates in Europe, Africa and Australia. All of the basins exhibit some form of non-stationary conditions, due, for example, to warming, droughts or land-cover change. The evaluation of the daily discharge simulations focuses on the overall model performance and its decomposition into three components measuring temporal dynamics, mean flow volume and distribution of flows. Calibration performance is similarly high as in previous COSERO applications. However, when looking at evaluation periods independent of the calibration, the model performance drops considerably, mainly due to severely biased discharge simulations in semi-arid basins with strong non-stationarity in rainfall. Simulations are more robust in European basins with humid climates. This highlights the fact that hydrological models frequently fail when simulations are required outside of calibration conditions in basins with non-stationary conditions. As a consequence, calibration periods should be sufficiently long to include both wet and dry periods, which should yield more robust predictions.     

Transfers and environmental co-benefits of carbon sequestration in agricultural soils: retiring agricultural land in the Upper Mississippi River Basin

This study investigates the carbon sequestration potential and co-benefits from policies aimed at retiring agricultural land in the Upper Mississippi River Basin, a large, heavily agricultural area. In addition to empirically measuring environmental co-benefits, we also compute economic transfers, which have sometimes been referred to as a co-benefit. Very little empirical work measuring the potential magnitude of these transfers has previously been undertaken. We compare and contrast alternative targeting schemes. We find that there are considerable amount of co-benefits and transfers and that the geographic distribution of co-benefits and transfers varies significantly with the specific benefit targeted. This implies that policy design related to targeting can have very important implications for both environmental conditions and income distributions in sub-regions. Issues related to policy design in the presence of co-benefits are considered. Senior authorship is shared equally between the first two authors. All views are those of the authors and not necessarily the funding agencies.     

Effect of subsurface drainage on runoff and sediment yield from an agricultural watershed in western Oregon,U.S.A.

Rainfall, watershed runoff and suspended-sediment concentrations for three small watersheds (0.46, 1.4 and 6.0 ha in size) were measured continuously for four winter rainfall seasons. The watersheds were fall-planted to winter wheat and were located on the hilly western margins of the Willamette Valley, Oregon. Following two rainfall seasons of data collection, a subsurface drainage system (consisting of a patterned arrangement of 10-cm plastic tubing at a depth of 1.0 m and a spacing of 12 m) was installed on the 1.4-ha watershed (watershed 2).Perched water tables were lowered and seepage was reduced on watershed 2 following the installation of the drainage system. The reductions were quantified with a water-table index (cumulative integrated excess). Watershed runoff and sediment yield from watershed 2 were decreased by ～65 and ～55%, respectively. These reductions were estimated from double mass curves and by statistical regression on a set of hydrograph variables. Maximum flow and average flow rates were decreased and the time from the beginning of a storm to the peak flow (lag time) increased.It is concluded that subsurface drainage can be an effective management practice for erosion control in western Oregon.     

Regulation of hepatic metallothionein in estradiol-treated rainbow trout

Metallothionein has previously been shown to be regulated during the period of exogenous vitellogenesis (Olsson et al. (1987); Fish Physiol, Biochem., 3(1), 39–47). Following estradiol injection of rainbow trout it has been shown that hepatic metallothionein remains at basal levels until the vitellogenin mRNA levels begin to decline and Zn is released from high-molecular-weight proteins (Olsson et al. (1989); Biochem.J., 257, 555–559), In the present study the effects of estradiol treatment on the metal-inducibility of metallothionein have been investigated. Estradiol-treated fish that were injected with low doses of cadmium or zinc did not respond by induction of metallothionein.