English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Tools annual

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

Massachusetts streams and stream basins have been subjected to a wide variety of human alterations since colonial times. These alterations include water withdrawals, treated wastewater discharges, construction of onsite septic systems and dams, forest clearing, and urbanization—all of which have the potential to affect streamflow regimes, water quality, and habitat integrity for fish and other aquatic biota. Indicators were developed to characterize these types of potential alteration for subbasins and groundwater contributing areas in Massachusetts. The potential alteration of streamflow by the combined effects of withdrawals and discharges was assessed under two water-use scenarios. Water-use scenario 1 incorporated publicly reported groundwater withdrawals and discharges, direct withdrawals from and discharges to streams, and estimated domestic-well withdrawals and septic-system discharges. Surface-water-reservoir withdrawals were excluded from this scenario. Water-use scenario 2 incorporated all the types of withdrawal and discharge included in scenario 1 as well as withdrawals from surface-water reservoirs—all on a long-term, mean annual basis. All withdrawal and discharge data were previously reported to the State for the 2000–2004 period, except domestic-well withdrawals and septic-system discharges, which were estimated for this study. The majority of the state’s subbasins and groundwater contributing areas were estimated to have relatively minor (less than 10 percent) alteration of streamflow under water-use scenario 1 (seasonally varying water use; no surface-waterreservoir withdrawals). However, about 12 percent of subbasins and groundwater contributing areas were estimated to have extensive alteration of streamflows (greater than 40 percent) in August; most of these basins were concentrated in the outer metropolitan Boston region. Potential surcharging of streamflow in August was most commonly indicated for main-stem river subbasins, although surcharging was also indicated for some smaller tributary subbasins. In the high-flow month of April, only 4.8 percent of subbasins and groundwater contributing areas had more than 10 percent potential flow alteration. A majority of the state’s subbasins and groundwater contributing areas were also indicated to have relatively minor alteration of streamflow under water-use scenario 2 (long-term average water use, including surfacewater-reservoir withdrawals). Extensive alteration of mean annual flows was estimated for about 6 percent of the state’s subbasins and groundwater contributing areas. The majority of subbasins estimated to have extensive long-term flow alteration contained reservoirs that were specifically designed, constructed, and managed to supply drinking water to cities. Only a small number of subbasins and groundwater contributing areas (1 percent) were extensively surcharged on a longterm, mean annual basis. Because site-specific data concerning surface-water-reservoir storage dynamics and management practices are not available statewide, the seasonal effects of surface-water-reservoir withdrawals on downstream flows could not be assessed in this study. The impounded storage ratio (volume of impounded subbasin or groundwater-contributing-area storage divided by mean annual predevelopment outflow from the subbasin or contributing area, in units of days) indicates the potential for alteration of streamflow, sediment-transport, and temperature regimes by dams, independent of water use. Storage ratios were less than 1 day for 33 percent of the subbasins and groundwater contributing areas, greater than 1 month for about 40 percent of the cases, and greater than 1 year for 3.2 percent of the cases statewide. Dam density, an indicator of streamhabitat fragmentation by dams, averaged 1 dam for every 6.7 stream miles statewide. Many of these dams are not presently (2009) being managed. The highest dam densities were in portions of Worcester County and in the PlymouthCarver region, respectively, reflecting the historical reliance of Massachusetts industry upon water power and agricultural water-management practices in southeastern Massachusetts. Impervious cover is a frequently used indicator of urban land use. About 33 percent of the state’s 1,429 subbasins and groundwater contributing areas are relatively undeveloped at the local scale, with a local impervious cover of less than 4 percent. About 18 percent of Massachusetts subbasins and contributing areas are highly developed, with a local impervious cover greater than 16 percent. The remaining 49 percent of subbasins and contributing areas have levels of 2 Indicators of Streamflow Alteration, Habitat Fragmentation, Impervious Cover, and Water Quality for Massachusetts urban development between these extremes (4 to 16 percent local impervious cover). Cumulative impervious cover, defined for the entire upstream area encompassed by each subbasin, shows a smaller range (0 to 55 percent) than local impervious cover. Both local and cumulative impervious cover were highest in metropolitan Boston and other urban centers. High elevated impervious-cover values were also found along major transportation corridors. The water-quality status of Massachusetts streams is assessed periodically by the Massachusetts Department of Environmental Protection pursuant to the requirements of the Federal Clean Water Act. Streams selected for assessment are commonly located in larger subbasins where some degree of impairment is expected. In the 72 percent of the state’s subbasins and groundwater contributing areas with assessed streams in 2002, more than 50 percent of the assessed stream miles were considered impaired. All of the assessed stream miles were considered impaired in 66 percent of the subbasins and groundwater contributing areas with assessed streams. Large streams, such as the main stems of rivers that make up most of the assessed stream miles, also are in many cases the receiving waters for treated wastewater discharges and for this reason may be more susceptible to water-quality impairments than smaller streams. Subbasins and contributing areas with large fractions of assessed stream miles that are listed as impaired are distributed across the state, but are more prevalent in eastern Massachusetts. Introduction Humans interact with streams and stream basins in a wide variety of ways. Such interactions include the withdrawal, discharge, and interbasin transfer of water and wastewater, dam construction and operation, stream channelization, urbanization and other types of land-cover change, and anthropogenic climate change (Vörösmarty and Sahagian, 2000; Milly and others, 2005; Walsh and others, 2005; Weiskel and others, 2007). Over time, human interactions with stream basins may alter streamflow regimes, water quality, and the integrity of aquatic habitats, affecting the availability of freshwater for human and ecosystem needs. In Massachusetts, concern has grown in recent years about all forms of basin alteration, the potential effects of basin alteration on water availability and aquatic habitat, and the need for improved indicators of basin alteration. In 2001, the Massachusetts Water Resources Commission (MWRC) developed an interim “stressed basin” classification, in order to “flag areas [in which proposed development projects] may require a more comprehensive and detailed review of environmental impacts or require additional mitigation” (Massachusetts Water Resources Commission, 2001). The stressed-basin classification was based on an analysis of electronically available streamflow data from 72 U.S. Geological Survey (USGS) gages in the state with more than 25 years of daily record. Three flow statistics—median annual 7-day low flow, median annual 30-day low flow, and the median annual low-flow pulse duration—were compiled for each gaging station and normalized to the basin drainage area at each station.1 The gaged basins were then ranked according to the magnitude of each statistic. A stress level was assigned to each gaged basin according to the relative ranking of the basin with respect to the three low-flow statistics. The 2001 Massachusetts stress classification was based entirely on streamflow data from gaged sites, because these were the only relevant data that were available statewide in electronic form at the time of the analysis. This approach imposed several limitations on the 2001 stress designations; these limitations were noted in the MWRC report (Massachusetts Water Resources Commission, 2001). First, the relative contributions of seasonal climate variation, natural basin characteristics, and human factors to streamflow variability could not be distinguished. Second, levels of flow alteration in ungaged basins could not be assessed. Finally, the 2001 report noted the importance of biological, water-quality, and land-cover indicators of basin alteration, but provided no information concerning these factors. Since 2001, data sets and computer tools have become available that allow several of these limitations to be addressed. For example, the USGS, in cooperation with the Massachusetts Department of Conservation and Recreation (MDCR), defined a set of 61 least altered or index streamgages across southern New England (Armstrong and others, 2008). This set of index stations defined the range of natural streamflow regimes in Massachusetts and informed the development of an index-streamflow guidance document (Massachusetts Water Resources Commission, 2008). In addition, the USGS, in cooperation with the Massachusetts Department of Environmental Protection (MDEP), recently developed a computer application for estimating both natural and water-useaffected daily streamflows at ungaged sites, facilitating statewide analysis of water use in relation to availability (Archfield and others, 2010). As part of this effort, a database of annually reported withdrawal information for public-watersupply sources an

Indicators of streamflow alteration, habitat fragmentation, impervious cover, and water quality for Massachusetts stream basins