These datasets represent aquatic core areas and aquatic buffers, in combination with terrestrial cores and connectors they spatially represent the ecological network derived from the CTR LCD project. All datasets in this map are included in the download.

River and Stream (lotic) cores:  This set of core areas, in combination with the lake and pond cores and terrestrial cores and connectors, spatially represent the ecological network derived from the CTR LCD project. The network is designed to provide strategic guidance for conserving natural areas, and the fish, wildlife, and other components of biodiversity that they support, within the Connecticut River watershed. Core areas serve as the foundation of the conservation design. They reflect decisions by the CTR LCD planning team about the highest priority areas for sustaining the long-term ecological values of the watershed, based on currently available, regional-scale information.

River and Stream cores represent the following:

1) streams of relatively high ecological integrity across all lotic (i.e., riverine) ecosystem types, emphasizing rivers and streams that are relatively intact (i.e., free from human modifications and disturbance locally and within the upstream catchments) and resilient to environmental changes (e.g., climate change). Integrity has the potential to remain high, both in the short-term due to the connectivity to similar natural environments within the riverine network, and in the long-term for headwater streams due to the relative insensitivity of stream temperature to air temperature changes;

2) headwater streams of relatively high current habitat value (i.e., landscape capability) forbrook trout, emphasizing streams that provide the best habitat conditions under current climate conditions; and

3) large and medium rivers that provide habitat for anadromous fish, including the portions of the mainstem and major tributaries of the Connecticut River from the mouth of the river upstream to the limit of passability for American shad, blueback herring, shortnose sturgeon, alewife, and sea lamprey.

Core areas are built from focal areas with high value based on one or more of the attributes listed above. These "seed areas" are expanded upstream and downstream to include areas that provide additional ecological value and resilience to long-term change and to encompass a minimum of 1 km in stream length. Consequently, the cores may include sections of lower-valued streams and extend beyond road-stream crossings; however, they do not extend past dams. Collectively, river and stream core areas encompass 28% of the total stream length in the CTR watershed, as decided by the partnership. A total of 523 lotic core areas have been identified, ranging in stream length from 1 to 442 km, with an average stream length of 16 km. 

The river and stream (lotic) core areas can serve as a starting point that can be used in combination with other sources of information to direct specific management and conservation actions or decisions. Although the lotic cores are presented as discrete entities, it is important to recognize that their boundaries are, in fact, "fuzzy" and are best interpreted as general places to focus attention. River and stream cores are not the only places of high ecological value within the riverine network deserving of conservation attention. Suggestions for combining this core network with other sources of information include: 

• Use in combination with the foundational data layers to identify additional areas of high ecological value. Layers to consider include: 1) aquatic ecosystem-based core area selection index, 2) index of ecological integrity, 3) USGS headwaters stream temperature tolerance index, and 4) brook trout current probability of occupancy. 

• Use in combination with landscape capability layers for other stream-dependent representative species, such as Louisiana waterthrush and wood turtle, to identify core areas with additional ecological value. 

• Use the aquatic buffers layer to identify places predicted to have a strong influence on the ecological integrity of the cores; i.e., places where anthropogenic disturbances may adversely affect the cores through watershed processes such as nutrification and sedimentation. 

• Use in combination with the dam removal impacts layer (see dams.shp) and culvert upgrade impacts layer (see culverts.shp) to identify places where the integrity of the aquatic cores is limited by dams and/or culverts, and thus may represent priorities for restoration.

Use of the aquatic core network should be done considering the scope and limitations of this dataset: 

• For convenience, the size of each core area is expressed in terms of stream length, but note that the core includes the entire shore-to-shore aquatic environment, and often encompasses or extends through adjacent wetlands and water bodies, as depicted in the ecological systems map.

• It is critical to remember that river and stream cores are in large part derived from the index of ecological integrity, which is scaled from relatively low to high separately for each ecological system within each HUC6 watershed. Consequently, the best areas available for each ecological system is captured by the cores. However, this does not mean that the areas selected are always unimpaired. For example, the best available area for a cool, medium-sized river may be quite degraded since these are areas that tend to be developed if not otherwise in conservation ownership.

Lake and Pond (lentic) cores: This set of core areas, in combination with the river and stream (lotic) cores and terrestrial cores and connectors, spatially represent the ecological network derived from the CTR LCD project. The network is designed to provide strategic guidance for conservation of natural areas, and the fish, wildlife, and other components of biodiversity that they support, within the Connecticut River watershed.  Core areas serve as the foundation of the conservation design. They reflect decisions by the CT River LCD planning team about the highest priority areas for sustaining the long-term ecological values of the watershed, based on currently available, regional-scale information. 

Lake and Pond cores represent the following:  

1)  lakes and ponds of relatively high ecological integrity, emphasizing lakes and ponds that are relatively intact (i.e., free from human modifications and disturbance locally and within the water body catchment) and resilient to environmental changes (e.g., climate change) due to their size and connectivity to similar natural environments.  

Lake and pond core areas are built from focal areas in ponds and lakes with high ecological integrity. These "seed areas" are expanded to include the entire water body in order to create logical conservation units. Consequently, the larger lake and pond cores may include partially-developed shorelines. Collectively, lake and pond core areas encompass 27% of the total area of ponds and lakes in the CTR watershed, as decided by the partnership. Note, Quabbin Reservoir, which itself comprises 20% of the total area of ponds and lakes in the CTR watershed, was not included as a core in this scenario. A total of 1,206 lake and pond core areas have been identified, ranging in size from 0.06 to 1,323 ha, with an average size of 11.7 ha. 

Considerations for Using Data Layer 

The lake and pond (lentic) cores are based on a simple classification of lentic systems into ponds (<8 ha) and lakes (≥8 ha) due to the lack of a more detailed classification at the time of this analysis. Thus, they do not account for other environmental factors, such as depth, trophic status, and water chemistry that can influence the composition, structure and function of lake and pond systems. In addition, there are no representative species included for lake and pond systems to complement the ecological integrity assessment. As such, the selection of lake and pond cores should be viewed as very preliminary and as an interim solution until a more detailed classification and assessment of lake and pond systems can be completed. Other suggestions include: 

• Use in combination with the index of ecological integrity to identify other ponds and lakes with high ecological value. DSL Project Component: Landscape Conservation Design Author: K. McGarigal Page 111 of 132 Updated on 13 October 2015 

• Use in combination with landscape capability layers for other lentic-associated representative species, such as moose and wood duck, to further understand the potential ecological value of the lakes and ponds. 

• Use in combination with the river and stream (lotic) cores to identify contiguous networks of high-valued lentic and lotic systems; i.e., places where lake and pond cores are connected to river and stream cores.

Aquatic buffers: This dataset buffers around the aquatic (stream and river  and lake and pond) cores. Aquatic buffers spatially represent the areas estimated to have a strong influence on the integrity of the aquatic cores based on watershed processes. Specifically, the buffers represent areas hydrologically connected to the aquatic cores through surface runoff and instream flow processes, such that anthropogenic stressors within the buffers are likely to adversely impact the integrity of the aquatic cores. Importantly, the buffers represent places upstream and upslope of the cores where human activities such as development, and point and non-point pollution, etc., may have a strong impact on the ecological condition of the cores. Unlike the cores, therefore, the buffers do not necessarily represent areas of high ecological integrity. Buffers are established for all aquatic cores (both river and streams and lakes and ponds) based on a time-of-flow model that extends as a gradient upstream and upslope from the cores, varying in distance depending on slope and land cover. Areas immediately upstream and upslope of the cores have the greatest influence (i.e., shortest time-of-flow). The influence decreases much faster across land than water so that the buffer typically extends much farther upstream than upslope from the core. Thus, the buffer does not represent a discrete zone distinguishing "inside" from "outside" of the buffer. Rather, it represents a graduated zone of influence in which cells upstream and closer to the core have greater influence. Cells in the upland and farther from the stream, especially on flat slopes with forest cover, have less influence. In addition, the graduated zone of influence increases in size with decreasing stream size. The zone of influence on larger rivers tends to be relatively narrow, whereas the zone of influence on headwater creeks tends to be wider and often encompasses the entire upstream catchment.

Considerations for Using Data Layer 

Overall, aquatic buffers are best interpreted as a way to focus attention on generally where in the watershed human disturbance will likely have the greatest influence on the integrity of the aquatic cores. Although the buffers are presented as an absolute gradient of decreasing influence with increasing distance upstream and upslope of the cores, it is important to recognize that the gradient depicted is relative. Moreover, the gradient is thresholded to extend progressively greater distances upslope on increasingly smaller streams. Because this graduated zone of influence can be difficult to visualize and interpret, it may be more useful to threshold the gradient at one or more levels to depict tiered zones of influence that are more akin to conventional fixed-width buffers. A suggestion for combining this dataset with another dataset in the package is: 

• Use in combination with the probability of development layer to identify places where development is both likely and predicted to have a strong influence on the ecological integrity of the aquatic cores, and thus may represent priorities for land protection and/or management. GIS Formats and Definitions DSL Project Component: Landscape Conservation Design Author: K. McGarigal Page 116 of 132 Updated on 13 October 2015 Geotiff raster (30 m cells); cell value = the magnitude of influence based on the time-of-flow model; values range from 1 (maximum influence) at the core to zero 0 (no influence) at the cell with the least influence (i.e., furthest upstream and upslope of the core).

River and Stream Network (Stream Class): a classified version of the stream network in which streams are classified and mapped along centerlines, even through wetlands and lake and pond systems, to provide a contiguous, classified stream network. This product differs from the ecological systems map in that this layer 1) is a vector versus raster representation of streams (i.e., lines versus cells) and 2) has streams classified as lake and pond systems throughout, whereas wetlands and river and stream systems take precedence in the ecological systems map. This layer is provided for the sole purpose of facilitating the display (in GIS) and mapping of landscape design products, as it is much easier to visualize vector features than raster features for narrow linear features such as streams. 

Considerations for Using Data Layer 

This layer is for the purpose of displaying the contiguous, linear stream network. Note, however, that centerlines through wetlands and lake and pond systems are evaluated as wetland and lake and pond systems, respectively, in the ecological assessment that forms the basis for the landscape conservation design. It may be useful in combination with the aquatic core area selection index, brook trout selection index, and USGS stream temperature tolerance index to better understand the ecological setting (i.e., lotic system) of any particular place that is evaluated with these additional products.