Modeling Pre‐ and Post‐Dam Removal Sediment Dynamics: The Kalamazoo River,Michigan1

Abstract:  The state of Michigan is interested in removing two low‐head dams in an 8.8 km reach of the Kalamazoo River between Plainwell and Otsego, Michigan, while minimizing impacts locally and to downstream reaches. The study was designed to evaluate the erosion, transport, and deposition of sediments over a 37.3‐year period using the channel evolution model CONCEPTS for three simulation scenarios: Dams In (DI), Dams Out (DO), and Design (D). The total mass of sediment emanating from the channel boundary, for the DI case, shows net deposition of 4,100 T/y for the study reach, with net transport (suspended and bed load) of 10,500 T/y passing the downstream boundary. For the DO case, net erosion is 19,200 T/y with net transport of 30,100 T/y (187% increase) passing the downstream boundary. For the D case, net deposition is 2,570 T/y (37% decrease) with transport of 14,200 T/y (35% increase) passing the downstream boundary. The most significant findings were: (1) removal of the low‐head dams will cause significant erosion of sediments stored behind the dams and increased sediment loads passing the downstream boundary and (2) sediment loads for the proposed channel design are similar to existing conditions and offer reduced fine‐sediment loadings.     

Artificial indoor streams as a method to investigate the impact of chemicals on lotic communities

The potential hazard of chemicals on aquatic communities are generally evaluated by standardised single-species bioassays. Safety assessment is based on results gained from organisms adapted to lentic systems and biological interactions in ecosystems are neglected. While lotic communities are often at first in contact with chemicals, it is astonishing that microcosms with lentic communities are mainly used as a bridge between laboratory bioassays and outdoor aquatic systems. Hence, we established five artificial indoor streams to simulate abiotic factors of small rivers. The closed-circuit system was filled with nutrients added to tap water. Washed pebbles were used as sediment. The dynamics of a simple biocoenoses consisting of aufwuchs, Lumbriculus variegatus Asellus aquaticus and Gammarus fossarum was investigated. The dynamic of aufwuchs and periphyton was determined as dry weight and chlorophyll-a, respectively and qualitatively by pigment pattern. The abundance of different developmental stages of L. variegatus was determined at the end of the experiment as well as the population dynamics of G. fossarum and A. aquaticus. Survival rates of gammarids and juveniles per female were investigated and data were used for modelling the population dynamics. The experiment was carried out to investigate the performance of the established artificial streams and the developed approaches to investigate effects of chemicals on a basic lotic community. The prime reason to establish this approach was to close a gap between complex artificial stream systems and laboratory single species tests to assess the impact of chemicals on the aquatic environment.     

Assessing Retrospective National Water Model Streamflow with Respect to Droughts and Low Flows in the Colorado River Basin

Streamflow monitoring in the Colorado River Basin (CRB) is essential to ensure diverse needs are met, especially during periods of drought or low flow. Existing stream gage networks, however, provide a limited record of past and current streamflow. Modeled streamflow products with more complete spatial and temporal coverage (including the National Water Model [NWM]), have primarily focused on flooding, rather than sustained drought or low flow conditions. Objectives of this study are to (1) evaluate historical performance of the NWM streamflow estimates (particularly with respect to droughts and seasonal low flows) and (2) identify characteristics relevant to model inputs and suitability for future applications. Comparisons of retrospective flows from the NWM to observed flows from the United States Geological Survey stream gage network over 22 years in the CRB reveal a tendency for underestimating low flow frequency, locations with low flows, and the number of years with low flows. We found model performance to be more accurate for the Upper CRB and at sites with higher precipitation, snow percent, baseflow index, and elevations. Underestimation of low flows and variable model performance has important implications for future applications: inaccurate evaluations of historical low flows and droughts, and less reliable performance outside of specific watershed/stream conditions. This highlights characteristics on which to focus future model development efforts.     

Nutrient Inputs to the Laurentian Great Lakes by Source and Watershed Estimated Using SPARROW Watershed Models1

Robertson, Dale M. and David A. Saad, 2011. Nutrient Inputs to the Laurentian Great Lakes by Source and Watershed Estimated Using SPARROW Watershed Models. Journal of the American Water Resources Association (JAWRA) 47(5):1011‐1033. DOI: 10.1111/j.1752‐1688.2011.00574.x Abstract: Nutrient input to the Laurentian Great Lakes continues to cause problems with eutrophication. To reduce the extent and severity of these problems, target nutrient loads were established and Total Maximum Daily Loads are being developed for many tributaries. Without detailed loading information it is difficult to determine if the targets are being met and how to prioritize rehabilitation efforts. To help address these issues, SPAtially Referenced Regressions On Watershed attributes (SPARROW) models were developed for estimating loads and sources of phosphorus (P) and nitrogen (N) from the United States (U.S.) portion of the Great Lakes, Upper Mississippi, Ohio, and Red River Basins. Results indicated that recent U.S. loadings to Lakes Michigan and Ontario are similar to those in the 1980s, whereas loadings to Lakes Superior, Huron, and Erie decreased. Highest loads were from tributaries with the largest watersheds, whereas highest yields were from areas with intense agriculture and large point sources of nutrients. Tributaries were ranked based on their relative loads and yields to each lake. Input from agricultural areas was a significant source of nutrients, contributing ～33‐44% of the P and ～33‐58% of the N, except for areas around Superior with little agriculture. Point sources were also significant, contributing ～14‐44% of the P and 13‐34% of the N. Watersheds around Lake Erie contributed nutrients at the highest rate (similar to intensively farmed areas in the Midwest) because they have the largest nutrient inputs and highest delivery ratio.     

Use of Small Forage Fish for Regional Streams Wildlife Risk Assessment: Relative Bioaccumulation of Contaminants

Selection of fish species for sampling to assess extent and potential effects of fish tissue contaminants is a criticalconsideration in the design of regional probability-designsurveys. The ideal species would be ubiquitous, bioaccumulatetoxic chemicals, and be prey of consumers of concern(piscivorous wildlife, humans). In first to third order streams,small short-lived forage fish (minnows (F. Cyprinidae), darters (F. Percidae), and sculpins (F. Cottidae), are more frequently found and therefore likely to be prey to more species ofwildlife than those of sportfish whose adults grow to a largesize (suckers (F. Catostomidae), trout (F. Salmonidae), bass, andsunfish (F. Centrarchidae), and carp). Targeting smaller foragefish should also produce a larger number of individuals persample on average than may be achieved with the larger species.An analysis of fish collected in 1993 and 1994 as part of theMid-Atlantic Highlands Assessment (MAHA) showed that, asexpected, forage fish were more ubiquitous than sportfishspecies. Analysis also revealed that, on a regional basis, forage fish bioaccumulated comparable levels to sportfish, ofsome widely occurring contaminants such as DDT, MeHg, and PCBs.Results indicated that smaller forage fish can be used asindicator species for a regional assessment for mostcontaminants (Zn being the one clear exception), that was notsignificantly different from one based on the larger species.Forage fish may therefore be an excellent choice as indicatorspecies for regional streams ecological risk assessment studies.     

人为干扰对川西亚高山针叶林土壤物理性质的影响

研究了川西亚高山针叶人工林在几种不同强度人为干扰下林地土壤物理性质。结果表明，随人为干扰强度的增加，土壤中细土（粉粒、粘粒）和大团聚体数量减少，小团聚体和原生土壤颗粒增加；土壤表层孔隙度减小，尤其是大孔隙明显减少；土壤有效水降低，持水供水能力减弱，渗透系数减小。川西亚高山人工针叶林土壤生态功能随人为干扰强度的增加而减弱，建议在最易受人为干扰的造林地区，最好是在造林初期封山育林。图1表5参13     

黄浦江水源地沉积物重金属潜在生态风险评价

为了解黄浦江上游饮用水源地沉积物中重金属的污染特征,对黄浦江干流和主要支流15个采样点的Hg、Cd、Pb、Cu和Zn含量进行检测,并对其生态风险进行评价.相比环境背景中位值,在15个样品中5种重金属含量都存在一定比例的超标现象,其中,Cd和Hg的污染相对明显;相比背景最大值,仅有Cu和Cd含量超标.采用潜在生态风险指数法和污染负荷指数法进行评价,所得出的生态风险等级均为无污染～中等污染水平,急水港近苏沪交界处、淀峰大桥、大蒸港沪浙交界处、大蒸港泖洋河交汇处、园泄泾以及五厍东一号河交界处区域生态风险较高,Cd和Hg是研究区域生态风险的主导因子.值得注意的是,黄浦江支流大蒸港和园泄泾的生态风险整体高于黄浦江干流.总体而言,黄浦江上游水源地表层沉积物中重金属污染仍处于中等以下水平.     

山西云顶山亚高山草甸优势种群和群落的格局分析

应用DCA排序与双项轨迹方差法相结合的方法,对云顶山亚高山草甸优势种群和群落的分布格局进行了分析.结果表明,群落格局与其优势种的格局关系密切,披针苔草 车前群系、披针苔草 蒲公英群系和嵩草 车前群系的格局差异明显,种群和群落的分布格局不仅受种的生物学特性影响,还受环境因子制约.图4表1参19     

ASSESSMENT OF PREDICTORS FOR STREAM EUTROPHICATION POTENTIAL1

ABSTRACT: Predicting stream eutrophication potential from non-point source nutrient loading across large temporal and spatial scales is a significant problem. In this paper we describe how two physiological indicators of P stress of stream bioflims, alkaline phosphatase activity (APA) and stored (surplus) P relate to two predictors of P loading: annual P loading predicted by the watershed model SIMPLE, and stream concentrations of soluble reactive P (SRP) in eight subbasins in the illinois River basin in Oklahoma. Data for APA, surplus P, nutrients and water chemistry were obtained at watershed outlets once during the cold season and twice during the warm season. There was a negative curvilinear relationship between APA and both predictors. Best fit was achieved by APA vs. annual predicted P loading. Both SRP and P. load are potentially useful to identify subbasins requiring no pollution abatement and to establish a regional target for P-load reduction. Surplus P is not as useful as APA in establishing these thresholds.     

Stream Phosphorus Transport in the Lake Tahoe Basin, 1989–1996

Lake Tahoe is undergoing the initial stages of culturaleutrophication due to human alteration of the airshed andwatershed. The lake's switch from nitrogen (N) to phosphorus (P)limitation has been attributed primarily to atmospheric Nloading. This places an increased importance on controllingwatershed movement of P to the lake. A stream water qualitymonitoring data set consisting of nine streams in the Lake Tahoebasin has been analyzed to characterize the spatiotemporalvariation of P delivery to the lake. This data is from the LakeTahoe Interagency Monitoring Program (LTIMP), which providesscientific data for planning and regulatory agencies to addressenvironmental problems in the Lake Tahoe basin. Results indicatethat P delivery (concentrations, loads) varies greatly atinterannual, seasonal, and spatial scales. Annual and seasonaltotal P (TP) concentrations can vary up to three orders ofmagnitude in a given stream and are strongly associated withsuspended sediment. Particulate P is the major form of Ptransported by Tahoe streams and was strongly correlated withpercent surficial geologic deposits, which are primarily locatednear streams. Tahoe streams with the highest annualP concentrations often had the lowest annual P loads, and visaversa. P loading is greatest during the spring snowmelt (75% ofannual average). Potential watershed parameters influencing Pdelivery to Lake Tahoe have been identified as precipitation,basin area, basin steepness, and road and human developmentcoverage. Results also suggest that human development impacts onstream P loads are most prevalent during high precipitationyears. Identification and quantification of stream sediment andP sources such as streambanks and impervious surface isnecessary to aid in watershed restoration efforts.