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63.
An index based method is developed that ranks the subwatersheds of a watershed based on their relative impacts on watershed
response to anticipated land developments, and then applied to an urbanizing watershed in Eastern Pennsylvania. Simulations
with a semi-distributed hydrologic model show that computed low- and high-flow frequencies at the main outlet increase significantly
with the projected landscape changes in the watershed. The developed index is utilized to prioritize areas in the urbanizing
watershed based on their contributions to alterations in the magnitude of selected flow characteristics at two spatial resolutions.
The low-flow measure, 7Q10, rankings are shown to mimic the spatial trend of groundwater recharge rates, whereas average annual maximum daily flow,
, and average monthly median of daily flows, , rankings are influenced by both recharge and proximity to watershed outlet. Results indicate that, especially with the higher
resolution, areas having quicker responses are not necessarily the more critical areas for high-flow scenarios. Subwatershed
rankings are shown to vary slightly with the location of water quality/quantity criteria enforcement. It is also found that
rankings of subwatersheds upstream from the site of interest, which could be the main outlet or any interior point in the
watershed, may be influenced by the time scale of the hydrologic processes. 相似文献
64.
A small, coastal stream in the San Francisco Bay area of California, USA, received the discharges from a drinking-water filtration plant. Two types of discharges were present. Discharges from filter backwashing were 3–4 times base stream flow, occurred 10–60 times per day, contained fine sediments, and each lasted about 10 min. The other discharge was a large, steady flow of relatively sediment-free water from occasional overflow of the delivery aqueduct which generally lasted several hours a day.Samples of invertebrates from natural substrates had significantly fewer taxa and lower density at the two stations below the backwash than at the two above. However, when stable artificial substrates were used, there were no significant differences among all four stations. The aqueduct apparently had no effect because the. invertebrate community at the station upstream of the backwash but downstream of the aqueduct was statistically similar to the station above the aqueduct. To test for acute toxicity, we exposed additional artificial substrates to short-term simulated backwash conditions. These exposures had no effect on invertebrate density or drift. Three-spine stickleback (Gasterosteus aculeatus) populations were also significantly reduced at the two downstream stations and were made up mostly of larger, adult fish. Prickly sculpins (Cottus asper), restricted to the most downstream station, were emaciated and had poor growth, probably as a result of scarce benthic food organisms. Artificial redds with eggs of rainbow trout (Salmo gairdneri) had significantly lower survival at two stations below the plant backwash (30.7% and 41.8%) than at the one above it (61.4%). Hatchery rainbow trout held in cages below the treatment plant from 7 to 37 days survived and continued to feed.Thus, the major effect of the water treatment plant on fish and invertebrates probably was not from acute toxicity in the discharges or the occasionally large discharge of clean water from the aqueduct, but was from the fluctuating backwash flows containing fine sediment that displaced small fish downstream and created unstable benthic substrates for invertebrates.The filter plant that we studied is a direct-feed type (that is, no sedimentation before filtration). These generally require greater frequencies of backwashing than do conventional plants and may therefore have greater biological impacts. Direct-feed plants are becoming increasingly popular throughout the world, for the most part because they are cheaper to build and operate. But if the associated biological problems are mitigated, then the cost savings of direct-feed compared to conventional plants may be lost. 相似文献
65.
苏州河沉积物中的硅藻及其污染指示作用 总被引:6,自引:0,他引:6
阐述了苏州河的北新泾处状沉积物中的硅藻丰度、种类及其数量的变化,优势种属的相对含量的变化。整段沉积物中上、中、下层硅藻的丰度、种类相对很少,苏州河一期污水截流工程建成后,水质有所改善,有利于藻类生长和繁殖,沉积下来的硅藻也增多。结果表明,该柱状沉积物中的硅藻变化能有效地反映苏州河的污染变迁趋势;苏州河的水质污染以前极其严重,近年来有所改善,其主要污染类型为有机污染。 相似文献
66.
苏州河纵向离散系数的分析研究 总被引:2,自引:0,他引:2
通过对苏州河水文水质资料的分析,并进行了水槽因子影响试验、非定常潮汐水流的模拟试验以及环境水力学理论分析和相似律推算,得到了比较符合实际的纵向离散系数取值范围:苏州河为单向流时K≈(5-35)m^2/s;苏州河在潮流往复作用下,k=(2-12)m^2/s。运用水质数学模型和苏州河实测的水文水质同步资料对纵向离散系数进行了验证。 相似文献
67.
68.
苏州河水量水质预报模型研究 总被引:8,自引:0,他引:8
根据建立的一维非恒定流水量模型和一维非稳态水质模型,定量预测苏州河在截污工程实施前后的水量和水质变化规律,探讨进一步改善苏州河水环境的措施。 相似文献
69.
运用系统工程方法对苏州河进行综合整治 总被引:3,自引:0,他引:3
从系统论的思想出发,提出苏州河水环境系统是由水的自然循环系统和水资源利用人工循环系统组成的复合生态系统,对这一系统的综合整治必须引进或采用系统工程的方法,文章对如何运用系统工程方法提出了构想,即一个苏州河水环境综合整治的基本模式:“:污染源-GIS-水质模拟-治理规划-工程措施-管理机制”。 相似文献
70.
略论影响苏州河水质的若干因素 总被引:2,自引:0,他引:2
苏州河(上海段)的水质受到不列因素的影响;1.源水水质,2.支流泄水;3.船舶污染;4.工厂废水,5暴雨溢流;6.农村排水;7.居民废物;8.底泥污染。在对这些影响因素分析的基础上,提出了一些解决设想。 相似文献