What Matters Most: Are Future Stream Temperatures More Sensitive to Changing Air Temperatures,Discharge, or Riparian Vegetation?

Simulations of stream temperatures showed a wide range of future thermal regimes under a warming climate — from 2.9°C warmer to 7.6°C cooler than current conditions — depending primarily on shade from riparian vegetation. We used the stream temperature model, Heat Source, to analyze a 37‐km study segment of the upper Middle Fork John Day River, located in northeast Oregon, USA. We developed alternative future scenarios based on downscaled projections from climate change models and the composition and structure of native riparian forests. We examined 36 scenarios combining future changes in air temperature (ΔT_air = 0°C, +2°C, and +4°C), stream discharge (ΔQ = ?30%, 0%, and +30%), and riparian vegetation (post‐wildfire with 7% shade, current vegetation with 19% shade, a young‐open forest with 34% shade, and a mature riparian forest with 79% effective shade). Shade from riparian vegetation had the largest influence on stream temperatures, changing the seven‐day average daily maximum temperature (7DADM) from +1°C to ?7°C. In comparison, the 7DADM increased by 1.4°C with a 4°C increase in air temperature and by 0.7°C with a 30% change in discharge. Many streams throughout the interior western United States have been altered in ways that have substantially reduced shade. The effect of restoring shade could result in future stream temperatures that are colder than today, even under a warmer climate with substantially lower late‐summer streamflow.     

合肥地区不同类型源头溪流暂态存储能力及氮磷滞留特征

为揭示合肥地区不同类型源头溪流暂态存储能力及氮磷吸收滞留的基本特征,在城区和城郊筛选4条典型源头溪流,并以NH4Cl、KH2PO4为添加营养盐,以Na Cl为保守型示踪剂,开展现场示踪实验.在此基础上,利用OTIS模型水文参数(D、A、As和α),计算暂态存储指标(Ts、Tc、Ls、Rh和F200med),进而开展暂态存储能力分析,并以NH+4-N和SRP一阶吸收系数(λ、λs)解析氮磷滞留特征.结果表明:4条溪流水体的α值均处于10-4~10-3数量级;各溪流Tc基本都显著超过Ts,意味着这些溪流水体溶质滞留效应主要来自主渠道流动水体,而不是暂态存储区;根据Tc、Ts、Ls和Rh等指标,得到各源头溪流暂态存储能力排序为:二十埠河二级支流二十埠河一级支流十五里河源头段关镇河支渠;4条源头溪流主渠道流动水体与暂态存储区的NH+4-N、SRP滞留特征存在很大的差异,并且二十埠河一、二级支流和十五里河均不同程度出现λ-NH+4、λs-NH+4为负值的现象,意味着这些水体对于NH+4-N既具有短期存储作用,也起着"源"的作用.     

Classification of Ephemeral,Intermittent, and Perennial Stream Reaches Using a TOPMODEL‐Based Approach

Whether a waterway is temporary or permanent influences regulatory protection guidelines, however, classification can be subjective due to a combination of factors, including time of year, antecedent moisture conditions, and previous experience of the field investigator. Our objective was to develop a standardized protocol using publically available spatial information to classify ephemeral, intermittent, and perennial streams. Our hypothesis was that field observations of flow along the stream channel could be compared to results from a hydrologic model, providing an objective method of how these stream reaches can be identified. Flow‐state sensors were placed at ephemeral, intermittent, and perennial stream reaches from May to December 2011 in the Appalachian coal basin of eastern Kentucky. This observed flow record was then used to calibrate the simulated saturation deficit in each channel reach based on the topographic wetness index used by TOPMODEL. Saturation deficit values were categorized as flow or no‐flow days, and the simulated record of streamflow was compared to the observed record. The hydrologic model was more accurate for simulating flow during the spring and fall seasons. However, the model effectively identified stream reaches as intermittent and perennial in each of the two basins.     

天山北麓宁家河阶地上的黄土堆积及其磁学特征

本文报道了新疆地区天山北麓宁家河阶地上的黄土堆积。研究剖面的两层黄土为河流 砾石层所隔开,这在新疆地区较为少见。通过系统的岩石磁学和粒度测量,分析了该剖面两层 黄土的磁学特征,并初步探讨磁化率变化机制。结果表明：黄土中的主要磁性矿物为磁铁矿和 磁赤铁矿,并含有少量赤铁矿和针铁矿。亚铁磁性矿物主要以多畴（MD）、假单畴（PSD）颗 粒为主,反映了这一地区极弱的成土作用。砾石层上下两层黄土磁学性质存在着差异,表现为 上层黄土具有较高的磁性矿物含量、较粗的磁颗粒和相对含量较高的软磁性矿物。下层黄土受 到后期河水的改造可能是导致这些差异的原因。磁化率与粒度呈现较好的正相关关系,与黄土 高原的情况相反,说明干旱地区的黄土磁学性质主要受原生磁性矿物控制。搬运风力和源区变 化是磁化率变化的主导因素。     

SEARCH: A GAGED WATERSHED INVENTORY1

ABSTRACT: A method, adapted to an APL interactive terminal, is described which allows the operator to thoroughly search a large set of gaged watersheds in order to find sources of comparable hydrologic data for detailed analysis. Bases of the search - and inventory - include drainage basin size and elevation, and geographical and temporal parameters, and should enhance opportunities for more reliable use of existing data.     

USING COMPUTED STREAM FLOW IN WATERSHED ANALYSIS1

Modifications in the computed climatic water budget have made it possible to achieve good agreement between computed and measured stream flow on both a monthly and annual basis in basins without appreciable winter snow cover. Comparisons of computed and measured stream flow in 28 basins on the Delmarva peninsula show that for some basins the agreement is excellent (regression line essentially equals unity), for other basins the regression line has a slope of one but it is displaced above or below the y=x line, while for other basins, the slope of the regression line differs appreciably from unity. Study of the basins where agreement between computed and measured values is only fair to poor reveals that the patterns of disagreement can be used to provide information on the water holding capacity in the root zone of the soil, on the quantity of deep aquifer recharge within the basin, or on the effect of human modifications within the basin. The technique should also reveal the quantity of interbasin transfers or other consumptive uses within the basin. The water budget, thus, becomes a useful tool to study hydrologic characteristics or their changes over time within a basin.     

THE EFFECTS OF MINE ACID ON THE POND RIVER WATERSHED IN WESTERN KENTUCKY1

ABSTRACT: H₂SO₄ (sulfuric acid) is formed by a chemical process that occurs in unreclaimed coal mines. The highly toxic acid then flows into the lower swamp areas where it causes considerable damage to the ecosystem. The major effect of the acid is the mass destruction of thousands of trees and various other phreatophytic plants. The contamination is so serious that most of the wildlife has migrated out of the affected area of the swamp in order to survive. Certain geological features such as coal bearing monadanocks make the area somewhat sensitive to mining activities and related geologic hazards. New methods of mine acid abatement make the concept of mass reclamation more realistic than at any time in the past. The constant annihilation of swamp life and processes emphasizes the urgent need for reclamation of the swamp.     

STREAM WASTE ASSIMILATIVE CAPACITY ANALYSIS USING REAERATION COEFFICIENTS MEASURED BY TRACER TECHNIQUES1

Atmospheric reaeration is a natural mechanism of oxygen transfer from the atmosphere to a water body. In practice, stream water quality models are developed with reaeration coefficients (K₂) estimated by predictive equations. This leads to uncertainties in modeling analysis because these equations are empirical in nature and may yield greatly different K₂ values for the same stream. Values of K₂ may be adjusted in model calibration, but unfortunately, values of other model parameters are no less easy to identify and require adjustment in model calibration as well. Therefore, validity of a stream model would be enhanced significantly if K₂ could be determined directly and reliably. In this research, values of K₂ in the Canandaiqua Outlet in Central New York have been measured by using a gas tracer method. A successful modeling analysis was conducted using these K₂ values. As a result, effluent limitations of several waste water discharges into the Outlet were established. It was concluded that field measurements of reaeration rate would improve modeling results significantly, and that the gas tracer method can be easily incorporated into intensive water quality surveys normally required for stream modeling.     

ORDER CLASSIFICATION OF URBAN CATCHMENTS1

ABSTRACT: Stream order systems provide useful classification methods according to the number of tributaries collected. In urban catchments, sewer line order is a concepot concept providing for the same type of classification. Horton's stream order system is used to classify sewers beginning with the smallest lines as first order to the largest main sewer which is sixth order for two catchments studied. Average tributary area, average length and number of lines are shown as functions of order. The bifurcation ratios are also presented. They can be used for finding the number of sewer lines in the next order. The number of first order lines depend on lot size and the bifurcation ratios vary widely.     

PROBABILISTIC METHODS IN STREAM QUALITY MANAGEMENT1

ABSTRACT. Recent advances in water quality modelling have pointed out the need for stochastic models to simulate the probabilistic nature of water quality. However, often all that is needed is an estimate of the uncertainty in predicting water quality variables. First order analysis is a simple method of providing an estimate in the uncertainty in a deterministic model due to uncertain parameters. The method is applied to the simplified Streeter-Phelps equations for DO and BOD; a more complete Monte Carlo simulation is used to check the accuracy of the results. The first order analysis is found to give accurate estimates of means and variances of DO and BOD up to travel times exceeding the critical time. Uncertainty in travel time and the BOD decay constant are found to be most important for small travel times; uncertainty in the reaeration coefficient dominates near the critical time. Uncertainty in temperature was found to be a negligible source of uncertainty in DO for all travel times.