IMPACTS OF CLIMATE CHANGE ON MISSOURI RWER BASIN WATER YIELD1

ABSTRACT: Water from the Missouri River Basin is used for multiple purposes. The climatic change of doubling the atmospheric carbon dioxide may produce dramatic water yield changes across the basin. Estimated changes in basin water yield from doubled CO₂ climate were simulated using a Regional Climate Model (RegCM) and a physically based rainfall‐runoff model. RegCM output from a five‐year, equilibrium climate simulation at twice present CO₂ levels was compared to a similar present‐day climate run to extract monthly changes in meteorologic variables needed by the hydrologic model. These changes, simulated on a 50‐km grid, were matched at a commensurate scale to the 310 subbasin in the rainfall‐runoff model climate change impact analysis. The Soil and Water Assessment Tool (SWAT) rainfall‐runoff model was used in this study. The climate changes were applied to the 1965 to 1989 historic period. Overall water yield at the mouth of the Basin decreased by 10 to 20 percent during spring and summer months, but increased during fall and winter. Yields generally decreased in the southern portions of the basin but increased in the northern reaches. Northern subbasin yields increased up to 80 percent: equivalent to 1.3 cm of runoff on an annual basis.     

INFLUENCES OF WATERSHED,RIPARIAN‐CORRIDOR,AND REACH‐SCALE CHARACTERISTICS ON AQUATIC BIOTA IN AGRICULTURAL WATERSHEDS1

ABSTRACT: Multivariate analyses and correlations revealed strong relations between watershed and riparian‐corridor land cover, and reach‐scale habitat versus fish and macroinvertebrate assemblages in 38 warmwater streams in eastern Wisconsin. Watersheds were dominated by agricultural use, and ranged in size from 9 to 71 km² Watershed land cover was summarized from satellite‐derived data for the area outside a 30‐m buffer. Riparian land cover was interpreted from digital orthophotos within 10‐, 10‐to 20‐, and 20‐to 30‐m buffers. Reach‐scale habitat, fish, and macroinvertebrates were collected in 1998 and biotic indices calculated. Correlations between land cover, habitat, and stream‐quality indicators revealed significant relations at the watershed, riparian‐corridor, and reach scales. At the watershed scale, fish diversity, intolerant fish and EPT species increased, and Hilsenhoff biotic index (HBI) decreased as percent forest increased. At the riparian‐corridor scale, EPT species decreased and HBI increased as riparian vegetation became more fragmented. For the reach, EPT species decreased with embeddedness. Multivariate analyses further indicated that riparian (percent agriculture, grassland, urban and forest, and fragmentation of vegetation), watershed (percent forest) and reach‐scale characteristics (embeddedness) were the most important variables influencing fish (IBI, density, diversity, number, and percent tolerant and insectivorous species) and macroinvertebrate (HBI and EPT) communities.     

NEAR‐STREAM LANDUSE EFFECTS ON STREAMWATER NUTRIENT DISTRIBUTION IN AN URBANIZING WATERSHED1

ABSTRACT: We investigated spatial and temporal relationships among surface and subsurface watershed attributes and stream nutrient concentrations in urbanizing Johnson Creek watershed in northern Oregon. We sampled stream water at eight urban and five nonurban locations from March 1998 through December 1999. We sampled eight wells distributed over the two primary aquifers in the watershed. Using a Geographic Information System (GIS), percentages of landuse attributes within a radius of 30, 91, and 152 m from each sample site were quantified. We analyzed relationships between (1) nutrient concentrations and percentage cover of different landuse attributes, and (2) nutrient concentrations and underlying hydrologic units. We did not find a significant relationship between ground water chemistry and stream water chemistry. We found elevated levels of phosphorus (P) concentrations correlated with urban landuse, while higher nitrogen (N) concentrations were correlated with nonurban (primarily agricultural) landuse. We concluded that elevated levels of N in nonurban areas of Johnson Creek watershed were associated with agricultural practices. We further concluded that urban development factors such as increases in storm drains, dry wells, and impermeable surfaces may be responsible for higher input of P to the stream in urbanizing areas of the Johnson Creek watershed.     

SAMPLING FRAME FOR IMPROVING PEBBLE COUNT ACCURACY IN COARSE GRAVEL‐BED STREAMS1

ABSTRACT: Improved sampling techniques are needed to increase the accuracy of pebble‐count particle‐size distributions used for stream studies in gravel‐bed streams. However, pebble counts are prone to operator errors introduced through subjective particle selection, serial correlation, and inaccurate particle‐size measurements. Errors in particle‐size measurements can be minimized by using a gravel template. Operator influence on particle selection can be minimized by using a sampling frame, 60 by 60 cm, in which sampling points are identified by the cross points of thin elastic bands. Serial correlation can be minimized by adjusting the spacing between the cross points and setting it equal to the dominant large particle size (=D₉₅). In a field test in a cobble‐bed stream, the sampling frame developed in this study produced slightly coarser size distributions, particularly in the cobble range, than the traditional heel‐to‐toe walk that selects particles with a blind touch at the tip of the boot. The sampling frame produced more similar sampling results between two operators than heel‐to‐toe walks. The difference between the two sampling methods is attributed to an unbiased selection of fine and coarse particles when using the sampling frame.     

大渡河上游地区景观格局与动态

利用卫星遥感资料,对大渡河上游地区金川、壤塘、马尔康三县18665km²土地的景观格局与动态进行分析。结果显示,1995～2000年,研究地区的景观破碎化程度有所下降,多样性增加,斑块形状不规则性增强。整个景观表现出以草地为基质,以林地变动为主要特征。5年间,有林地面积减少53687hm²,大部分转变为灌木林地和疏林地。有林地的空间动态,如斑块密度下降,形状趋于规则等,显示该地区森林减少主要是有计划采伐的结果。耕地面积的下降则表明当地退耕还林、还草的政策措施已初见成效。     

水体交换与传输的时间维特征

从水体交换时间维的特征出发对相关概念进行了总结,分析了宏观概念、微观概念的意义,比较了不同概念的异同。重点给出了更替周期及更新时间的计算方法,并分析了两者的关系。还参照前人研究,分析了水体入口、出口位置不同时水体更替周期、平均传输时间、平均寿命、平均滞留时间的关系。最后以20世纪90年代黄河中下游河段为例对其更替周期及逐月变化规律进行了计算分析,并证实径流量与更替周期存在负相关关系。     

岷江上游生态环境建设与经济可持续发展

岷江上游生态环境问题严重,森林破坏、植被生态功能退化、水土流失、生物多样性减少。在上游地区应加强退耕还林还草,建立生态型持续农业系统和生态文明示范区,调整产业结构,提高群众的综合素质,走可持续发展道路。     

小东江底泥中挥发酚的垂向分布研究

将沿小东江流域布点采集到的底泥样,根据其理化性质,从上到下分为A(0～10cm)、B(10～20cm)、C(20～35cm)、D(35～65cm)层,分析发现:挥发酚含量B>A>C>D层;A～D层挥发酚含量最高点分别对应的是细砂土、面砂土、砂粘土和面砂土.      

伊犁河水质的综合评价及分析

通过对伊犁河多年水质监测资料统计分析 ,对其进行了综合评价。分析比较了各断面、各水期的水质综合指数及年际变化 ,掌握了伊犁河水质分布规律、年际变化与污染物排序 ,以及伊犁河水质污染状况。     

UNCALCULATED IMPACTS OF UNSUSTAINABLE AQUIFER YIELD INCLUDING EVIDENCE OF SUBSURFACE INTERBASIN FLOW1

ABSTRACT: Unsustainable withdrawals from regional aquifers have resulted in adverse impacts considerable distances from the point locations of supply wells. In one area of the southeastern (SE) Coastal Plain, conservative estimates for repair/replacement of some residential wells damaged or destroyed by unsustainable yield from the Floridan aquifer system exceeded $4 million. However, a comprehensive assessment of damage/economic loss to private property and public resources due to unsustainable yield from that regional karst aquifer has not been made. Uncalculated direct costs to home‐owners from damage attributed to those withdrawals are associated with destruction of homes from increased sinkhole formation, devalued waterfront property, and removal of diseased and dead trees. Examples of other uncalculated economic burdens resulting from unsustainable aquifer yield in the SE Coastal Plain include: (1) irreversible damage to the aquifer matrix and concomitant increased potential for groundwater contamination, (2) large‐scale wildfires with subsequent degradation of air quality, debilitation of transportation corridors, and destruction of timber, wildlife habitat and property, and (3) destruction of “protected” natural areas. This paper provides a general background of the regional Floridan aquifer system's karst characteristics, examples of known impacts resulting from ground water mining in the SE Coastal Plain, and examples of additional damage that may be related to unsustainable yield from the Upper Floridan aquifer. Costs of these impacts have not been calculated and are not reflected in the price users pay for ground water. Evidence suggests that the classic watershed management approach must be revised in areas with mined regional karst aquifers to include impacts of induced recharge from the surficial aquifer, and subsurface inter‐basin flow. Likewise, associated impacts to surface water and interrelated systems must be calculated. The true cost of groundwater mining to this and future generations should be determined using a multidisciplinary approach.