Trout Population Responses to Restoration of Stream Flows

There are numerous demands for the limited water supplies in the Rocky Mountain (USA) region, and controversies surrounding instream flows abound. A specific problem involves water diversions (i.e., small dams that shunt water out of stream channels) during the summer irrigation season. We developed an approach to assess the effects of restoration of natural or less-than-natural summer flows on trout that accounts for variation in habitat over long segments of low-gradient, alluvial-valley streams. The approach has utility for managers because it can be conducted with hydologic data, aerial photographs, topographic maps, and a spreadsheet without extensive fieldwork. We applied the approach by assessing the effects of different summer flows on abundance of brown trout (Salmo trutta) in several streams annually dewatered in the Salt River Valley of western Wyoming. The assessment approach can be calibrated for other trout species and areas of the Rocky Mountain region.     

华北地区干旱强度的表征形式及其气候变异

在分析1951-2001年华北地区降水量、气温及蒸发量变化特征的基础上,确定利用月降水量与蒸发量之差的Z指数表征干旱强度.该指数在时间及空问分布上的实际概率与理论概率均很接近,可以较好地表征华北地区干旱强度状况.分析表明,华北地区干旱强度不但具有显著的年代际变化特征,且年际振荡的信号也很强.华北地区四季的干旱强度变化在干旱期的开始时间、干旱持续时间和干旱强度等方面存在一定的差异.     

Farmer decision making and spatial variables in northern Thailand

This research has two interrelated objectives. The first is to determine the extent to which a relationship exists between farmer characteristics and farming practices in three villages in northern Thailand. The second is to use standard statistical methods for incorporating spatial variables into the analysis and to assess the effects of these variables on farmer decision making. The data base includes information on the location and size of villages, roads, streams, and fields; a digital elevation model with information on elevation, slope, and aspect; and information keyed to individual fields on crops and cropping methods and the ethnicity, income, and religion of farmers. The map data (517 plots) were entered into a computerized geographic information systems (GIS). Results suggest several hypotheses about the relationships between land use and owner characteristics. More significantly, the study concludes that spatial analysis appears to be most useful when the dependent variable is either continuous or ordinal. The outlook is not quite as optimistic when the dependent variable is a nonordinal categorical variable. Before spatial analysis can be applied regularly to social science data, better computational tools need to be developed.     

General concepts for measuring cumulative impacts on wetland ecosystems

Because environmental impacts accumulate over space and time, analysis is difficult, and we must incorporate the most recent scientifically defensible information and methods into the process. Methods designed to deal specifically with cumulative impacts include checklists of characteristics or processes, matrices of interactions (rated according to their level of importance) between disturbance activities and environmental conditions, nodal networks or pathways that depict probable effects of disturbances, and dynamic system models. These methods have been tested over the past decade and have proven generally successful.Landscape perspectives have emerged as especially helpful in analyzing cumulative effects, and have focused specific attention on questions of spatial and temporal scale, while leading to recognition of the complexity of ecosystem processes in general. An evaluation of several cases studies by the Commission on Life Sciences of the U.S. National Academy of Sciences emphasizes the importance of interactions and cumulative effects, but recognizes that current knowledge of the processes involved is insufficient to make specific recommendations for conceptual frameworks.The conceptual approach suggested by Preston and Bedford (1988) addresses many critical issues, such as the need to define dimensions of scale, and the importance of wetland size, shape, and location in the landscape. This approach and similar ones must be tested and evaluated so that a consensus may eventually emerge.A cumulative impact matrix is proposed that sets up additive, synergistic, and indirect categories, each capable of variation in space and time. Every interaction would be carefully examined to determine the likelihood of cumulative impact in any of the six categories. Because of its magnifying glass approach, such a matrix could be a very useful analytical tool, using existing methods to uncover all the information presently available about the behavior of the ecosystem of concern.     

SEASONAL PUMPING VARIATION EFFECTS ON WELLHEAD PROTECTION AREA DELINEATION1

ABSTRACT: Delineation of a welihead protection area (WHPA) is the key element in welihead protection programs for drinking water supplies. WHPAs are often delineated under idealized conditions using simple steady-state assumptions, which lead to an incorrect estimation of area and geometry. In this paper, we compare the results from a simple steady-state procedure commonly employed in WHPA delineation with a more complex transient approach that allows consideration of seasonal variation in pumping rates. We also introduce a transient procedure to delineate time-related capture zones using a numerical ground water flow and transport model. Welihead delineation is examined for two municipal wells in Tipton, Oklahoma, using a ten-year time-of-travel criterion. In the steady-state procedure, where we assumed constant pumping rates, we used GPTRAC, a semi-analytical model, and MOC, a numerical model. The capture zone delineated by GPTRAC is comparable in shape with the capture zone delineated by MOC but not in size due to the differences in solution schemes. In the transient procedure, we used MOC and considered the seasonal variation in pumping rates. The capture zones delineated in this procedure were larger than the capture zones delineated by the steady-state procedure using the same model. Further analysis showed that a higher drawdown was predicted in the transient procedure than in the steady-state procedure, which is the reason for larger capture zones.     

SOURCES OF VARIABILITY IN PHOSPHORUS AND CHLOROPHYLL AND THEIR EFFECTS ON USE OF LAKE SURVEY DATA1

Summer lake survey measurements of total phosphorus (TP) and chlorophyll a (CHLa) from 188 reserviors and natural lakes in the midwest were analyzed to determine the magnitude of major sources of variability. Median variance among replicate samples collected at the same location and time was about 7-8 percent of the mean for both TP and CHLa. Median observed temporal variability within summers was 27 percent of the mean for TP and 45 percent of the mean for CHLa. Median values of year-to-year variance in average TP and CHLa were 22 percent and 31 percent of the mean, respectively. A range of approximately two orders of magnitude was observed among individual estimates of variance in each of these categories. The magnitude of observed temporal variability was affected only slightly by variance among replicate samples on individual days and was weakly correlated with the length of time during which samples were collected from individual lakes. Observed temporal variation was similar between reservoirs and natural lakes when variances were calculated with logtransformed data. The magnitude of temporal and year-to-year variance can severely limit the power of statistical comparisons of TP and CHLa means, but has less effect on establishing relative rankings of lake means, Sources and relative magnitude of variability are important in the use of TP and CHLa data in regression models and in the planning of lake surveys and subsequent data analysis.     

Nutrients Seasonal Variation and Budget in Jiaozhou Bay,China: A 3-Dimensional Physical–Biological Coupled Model Study

A 3-D biological model was developed and coupled to a hydrodynamic model, i.e., Princeton Ocean Model, to simulate the seasonal variation and budget of dissolved inorganic nitrogen, phosphate, and silicate in Jiaozhou Bay. The modeled nutrients distribution pattern is consistent with observation. Silicate, the most important limiting element for phytoplankton growth, is characterized by consumption in spring, increase in summer and autumn, and accumulation in winter, whereas dissolved inorganic nitrogen and phosphorous have increasing trend with low rates in spring, due to excessive river loads. Phytoplankton plays an important role in nutrient renewal by photosynthesis and respiration processes. During an annual cycle, 7.83 × 10³ t N, 0.28 × 10³ t P, and 3.93 × 10³ t Si are transported to the bay’s outer sea, i.e., the Yellow Sea, suggesting that Jiaozhou Bay is a significant source of nutrients for the Yellow Sea. The spatial distribution of nutrients is characterized by vertically homogeneous profiles, with high concentration inside the bay and low concentration toward the bay channel. These features are mainly governed by strong turbulent mixing, fluvial influx, water exchange rate, and Yellow Sea water intrusion. Numerical experiments suggest that the government should pay enough attention to proper layout of sewage drainage.     

近48年来广东春旱的变化

为了更好地做好广东省春旱的短期气候预测，用EOF分析、小波分析和相关分析等方法，对近48年（1957—2004年）来广东受害较大的春旱（2—5月）的变化规律及其成因进行了研究。结果表明，广东春季降水具有明显的2～3年和4年左右的年际变化以及36年左右的年代际变化。春旱主要发生在1960—1971年和1994—2004年，20世纪90年代以来严重春旱的发生呈增多趋势。1976／1977年之后，阶段性的冷与涝、暖与旱相对应，而其之前的这一相关性则不好。广东春季降水的异常主要与极涡、西太平副热带高压的强弱、亚洲大陆及其以北的500hPa环流异常有关。异常春早年500hPa同期环流场上极涡较强，偏向鄂霍次克海，亚洲大陆及其以北为明显的正高度距平，冷空气的活动偏强，副高偏东偏弱。850hpa流场上广东到南海盛行偏北气流，不利于降水的产生。异常涝年的情况则基本相反。     

Population Analysis of Sables in the Ural–Ob Region of the Species Range

An attempt at population analysis of sables in the Ural–Ob region of the species range was made with the use of vast biological material (craniometry, 1909 specimens; ecological structure, 2157 specimens; and coat color, 439169 pelts). Population groups in the region were mainly described on the basis of morphological, geographic, historical, and ecological criteria. Seven spatially separated population groups were found, which were named after the main rivers of their habitats: the Tavda–Konda–Sos'va, Dem'yanka, Salym–Yugan, Agan–Vakh, Kazym–Nazym, Nadym–Kunovat, and Pur–Taz groups. They distinctly differed from one another with respect to cranial measurements, coat color, and some structural demographic parameters. In some cases, morphological differences reached the subspecies level. The data obtained make it possible to revise the pattern of geographic variation within the species range.     

月亮泡底泥中元素的分布及其生态风险评价

对吉林省西部月亮泡底泥中元素的空间分布、来源以及重金属的潜在生态风险进行了研究。与吉林省中西部土壤中元素平均值相比,月亮泡表层底泥中明显富Hg、Pb、Ca、N,而相对贫As、Co、Mn、Th、Cl、Na。在湖底表层底泥中,As、Hg、U、Cd、Cu、Zn、Cr、Se、Mo、Co、Ni、Mn、N、P、MgO、Fe2O3、CaO、有机碳与Al2O3呈明显的正相关关系,表明它们的地球化学性质与粘土矿物的含量密切相关。表层底泥中Hg、Cd、As、Cr、Cu、Zn、Pb的潜在生态危害性均很小。在月亮泡的两个沉积柱中,元素含量随深度的变化不尽相同。在沉积柱1中,Fe2O3、Mn、P、Zn、Cu、Ni、Co、Cr、Cd等元素含量随深度变化不大,表明其沉积环境较为稳定。在沉积柱2中,元素含量波动较大,表明该沉积柱的沉积环境较为动荡,并在76～80cm和104～108cm处,As、Fe2O3、Mn、P、Cu、Zn、Co、Ni、Cd、Th、U等含量急剧增高;在70～90cm处Mn/Fe比值高,表明当时干旱少雨、沉积环境较为氧化,在104～108cm处Rb/Sr比高,可能反映当时高温多雨、化学风化作用较为强烈。两个沉积柱的Cr/Th比基本相似,表明沉积柱的物源基本相同。沉积柱中重金属的潜在生态危害程度也很小,表明从垂向上进入月亮泡水体的重金属污染物数量也很少。