CRBCZO -- Stream Water Chemistry, Stream Ecology -- USGS -- Chester County, PA -- (1998-2013)

Since 1969, the U.S. Geological Survey and the Chester County Water Resources Authority have conducted a cooperative program to evaluate stream ecology and water-quality conditions using benthic macroinvertebrates and stream-water chemistry. The Stream Conditions of Chester County Program has sampled streams every fall for over 30 years. The initial goals of the program were to evaluate stream-water quality and to further the understanding of changes in the stream ecosystem in response to urbanization. The current goals of the program are to use the data to monitor current conditions and determine trends. Data from the program have been used to help support Chester County Landscapes by providing information on biological diversity and water-quality conditions. Without monitoring it is impossible to determine if changes in land use or environmental policies and regulation are having a positive affect on water quality.

Benthic macroinvertebrates are macroscopic animals that inhabit the bottoms of aquatic habitats. Freshwater forms include aquatic insects and other invertebrates including clams, crustaceans, snails, and worms. Factors such as streamflow, food availability, habitat, temperature, and water quality determine the makeup of the macroinvertebrate community. By sampling in similar habitats with similar physical conditions, water quality becomes the determining factor controlling community structure. Changes in abundance, diversity, species richness, and presence or absence of pollution tolerant or intolerant species can be measured and related to water quality. Trends in water quality can be determined by sampling at a single location over several years and observing changes to the community structure.

Benthic macroinvertebrates are well suited as water-quality indicators because of their biology and availability. They are present in most aquatic systems and are relatively easy to collect. They are indicators of overall water quality and can be used to identify specific types and sources of degraded water quality. Benthic macroinvertebrates have limited mobility and cannot avoid poor water-quality conditions. They are sensitive to a wide range of environmental impacts including chemical and physical impairments.

Biological samples collected for the Stream Conditions of Chester County Biological Monitoring Network consist of benthic macroinvertebrates collected from a riffle area of the stream. A riffle habitat is used because macroinvertebrate diversity and abundance is usually highest there.

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自1969年以来，美国地质调查局和切斯特县水资源管理局共同开展了一项合作项目，旨在通过底栖大型无脊椎动物和溪流水化学成分评估溪流生态和水质状况。切斯特县溪流状况项目已连续30多年在秋季对溪流进行采样。该项目的初始目标在于评估溪流水质，并进一步增进对城市化对溪流生态系统变化影响的理解。当前的目标则是利用这些数据来监测当前状况并确定趋势。该项目收集的数据已被用于支持切斯特县景观，提供有关生物多样性和水质状况的信息。若不进行监测，则无法确定土地利用变化或环境政策与法规的变化是否对水质产生了积极影响。

底栖大型无脊椎动物是栖息于水生环境底部的宏观动物。淡水形态包括水生昆虫和其他无脊椎动物，如蛤蜊、甲壳类、蜗牛和环节动物。溪流水量、食物可获得性、栖息地、温度和水质量等因素决定了底栖大型无脊椎动物群落的结构。通过在相似栖息地中采集具有相似物理条件的样本，水质量成为决定群落结构的决定性因素。可以通过测量丰度、多样性、物种丰富度以及污染耐受或不耐受物种的存在与否来评估与水质量相关的变化。通过在单一地点连续多年的采样并观察群落结构的变化，可以确定水质量的变化趋势。

底栖大型无脊椎动物因其生物学特性和可获得性而非常适合作为水质指标。它们存在于大多数水生系统中，且相对容易采集。它们是整体水质量的指示器，可用于识别特定类型和来源的水质退化。底栖大型无脊椎动物活动能力有限，无法避免水质较差的环境。它们对广泛的生态环境影响敏感，包括化学和物理损害。

切斯特县溪流状况生物监测网络收集的生物样本包括从溪流急流区采集的底栖大型无脊椎动物。选择急流区栖息地是因为那里的底栖大型无脊椎动物多样性和丰度通常最高。

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