**2.5 Indicators of condition: biological quality**

*Water Quality - Science, Assessments and Policy*

laboratory protocols [32, 37]. Standardization allows the data to be combined to produce a nationally consistent assessment. Standardization also allows comparison to other methods. The 2004 survey provided an opportunity to examine the comparability of different sampling protocols by applying both the NRSA method and

The NRSA transforms the collected data into "indicators" that are meaningful to the public or can be translated into meaningful statements for the public. For example, over 3000 measurements of physical habitat structure are collected from each sample site and ultimately compacted into four indicators that can be meaningful to the public. Similarly, at each site the benthic macroinvertebrate and fish samples collected are reduced to a list of species present and their relative abundance. This information is then transformed into three indices of biotic integrity,

Setting reasonable expectations for each indicator is among the greatest challenges in assessing ecological condition [40, 41]. For the NRSA, ecological condition assessments based on chemical, physical, and biological field measurements at each site were compared to a benchmark of what one would expect to find in relatively undisturbed streams and rivers within that region [42]. Sets of least disturbed reference sites within each region were used to: (1) develop and calibrate multimetric indices (MMIs) and observed/expected (O/E) indices, and (2) set thresholds for three condition classes: good, fair, and poor [42]. Conditions at these sets of relatively undisturbed stream and river sites are called "reference

Rather than relying solely on best professional judgment to set these reference condition benchmarks or even to finalize the sites considered least disturbed/reference, the NRSA data analysts first generated a pool of candidate sites that might potentially serve as least disturbed reference. Candidate sites for this reference pool came from either hand-selected sites recommended by State and EPA Regional participants or were screened as a subset from the pool of sites selected using the probability design site selection process. The only requirement was that site-specific data be available. This reliance on data for the final determination of reference sites rather than solely relying on best professional judgment as recommended in the application of Tiered Aquatic Life Use (TALU) framework and the biological condition gradient [43] is one of the hallmarks of NARS – the use of data-driven

The pool of candidate reference sites was filtered through a set of physical and chemical data screens (i.e., riparian condition, nutrients, chloride, turbidity, excess fine sediments). When a site passed through all the data screens it was used to describe the distribution of condition indicators among least disturbed sites in that region (i.e., regional reference condition) "Pristine" landcover in watersheds was not required for a site to be considered "reference"; for example, sites in humanuse dominated watersheds with local chemical and physical conditions among the best in the region could still be considered reference. The use of biological data for screening was avoided over concerns of circularity. For the same reason, physical habitat observations (e.g., riparian vegetation and streambed sediments) other than direct observations of human activities were not used to screen candidate reference

Not every reference site had identical chemical, physical, biological indicator scores. A range of values was found at the reference sites within an ecoregion. This range of values was used to construct a reference site distribution. The 5th and

various state or USGS methods to a subset of the sites (e.g., [38, 39]).

one for the fish and two for the macroinvertebrates.

**2.4 Setting expectations: reference conditions**

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conditions".

determinations where possible.

sites for assessing physical habitat condition.

Samples of the macroinvertebrate and fish assemblages formed the basis for assessing the biological quality of streams and rivers. Only the macroinvertebrate assemblage results are presented here, although similar results are available for fish. Diatom assemblage samples were collected and analyzed and as of this writing, and taxonomic consistency issues are being resolved.

Two measures of the macroinvertebrate assemblage were used to communicate biological quality: a multimetric index (MMI) of macroinvertebrate integrity [10] and an observed/expected (O/E) index of taxa loss [11]. The MMI was developed for each of the nine aggregated ecoregions and compared with the reference conditions determined for that ecoregion [42].

O/E indices of taxa loss were also calculated. These are interpreted as the percentage of the expected taxa present at a site. Each tenth of a point less than 1 represents a 10% loss of taxa, e.g., an O/E value of 0.9 indicates 90% of the expected taxa are present and 10% are missing. Three O/E models were developed, one for each of the major climatic regions (**Figure 2A**): The Eastern Highlands, the Plains and Lowlands, and the West [11, 44]. Four categories of taxa loss were calculated: < 10% loss, 10–20% loss, 20–50% loss, and >50% taxa loss.

## **2.6 Indicators of stressors impacting streams and rivers**

River and stream biota can be adversely impacted when alterations occur within the watershed or within the stream and river itself. The in-stream and riparian characteristics that are altered as a result of human activity and in turn result in biotic changes are considered "stressor indicators". These resulting aquatic stressors can be chemical [45], physical, or in some cases, biological [46]. Importantly, the goal of the CWA is to restore and maintain the chemical, physical, and biological integrity of the nation's water resources. The NRSA has a dual purpose in generating data on chemical, physical, and biological stressors. The first purpose uses these data in describing chemical and physical integrity of rivers and streams as a means of tracking progress toward the goals of the CWA. The second purpose uses these data to rank the stressors in their relative importance for policy. Ranking occurs in three ways. The first way establishes how widespread the stressors are. The second way ranks stressors by their severity when they occur, i.e., how likely are they to impact biota. And the third way, perhaps the most important, ranks stressors based on the likely improvement in rivers and streams if that stressor is reduced or eliminated. Not every potential chemical or physical stressor is currently included in the NRSA reports on condition, but both present and future surveys of rivers and streams in the US should include measurements that enable assessments of additional stressors for which there is reasonable concern that they may become important in the future.

The NRSA stressor indicators are the proximal stressors, i.e., changes in chemical or physical attributes that can affect biota. The stressors are not the more distal measures such as basin land-use or land-cover alterations not directly observed by the field crews, e.g., row crops, mining, or grazing visible in satellite imagery. This approach asserts that many human activities on the landscape can be sources of pollutants or indirect causes of stress to streams. However, the focus of the NRSA is to identify and quantify the stressors, rather than their sources. The general

philosophy was to understand the most significant stressors first. This information can be used in the process of source tracking and determining probable causes, which are logical future steps for the NRSA and similar national assessments.

Eight stressor indicators were selected for reporting. Four stressors were chemical, and four were related to habitat alterations. The chemical stressors were excess total nitrogen (total N), excess total phosphorus (total P), excess salinity (based on conductivity), and acidification (based on acid neutralizing capacity). Prior 305(b) reports from States or national attention were the basis for these selections. Indicators of habitat alteration have not historically been included in monitoring by most water quality agencies. With a focus on the CWA goals, physical integrity became a needed element within NARS. Four indicators of physical integrity, excess fine sediments, alterations of instream fish habitat, alteration of riparian vegetation structure, and disturbance of the riparian zone are the initial focus. A fifth, hydrologic alteration is near completion.

#### **2.7 Ranking of stressors: relative extent and relative risk**

An important prerequisite to making policy and management decisions is an understanding of the relative magnitude or importance of potential stressors across a region and the expected benefit of reducing or eliminating that stressor. Both the prevalence (i.e., extent of stream length with high levels of the stressor) and the severity (i.e., impact on biological condition) of each stressor were considered. The NRSA reports include separate ranking for each of these elements, extent and risk.

Relative extent is a measure of how widespread the problem is…how much of the river and stream length has high levels of that particular stressor. Does high nitrogen occur in few or in many streams and rivers? Are high nitrogen levels geographically isolated or widespread? Relative risk, on the other hand, addresses the severity of the impact of high nitrogen on the biota when it occurs as compared to when nitrogen levels are low. Neither of these measures individually is a good indication that the problem should be addressed. But when combined, they provide powerful evidence of the need to act.

## **3. Results**

Fish, macroinvertebrates and periphyton samples were all collected during the 2013–2014 stream and river survey. The data were processed and assessed and can be found in the detailed online dashboard and report [47]. Here we present the results for just the macroinvertebrate assemblage as an example of data generated by the NRSA.

#### **3.1 Benthic macroinvertebrate conditions (MMI)**

Nationally, 44% of the perennial stream and river length (hereafter simply referred to as "stream length") was in poor condition, and 26% was in fair condition as measured by the benthic macroinvertebrate MMI relative to the least-disturbed reference condition in each of the nine aggregated ecoregions (**Figure 3**). Based on the MMI, 42% of stream length in the Eastern Highlands, 47% of stream length in the Plains and Lowlands, and 31% of stream length in the West were in poor condition. Detailed examples of results for the nine aggregated ecoregions for the 2008–2009 NRSA are available elsewhere [28, 48].

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*DOI: http://dx.doi.org/10.5772/intechopen.92823*

**3.2 Benthic macroinvertebrate taxa (O/E index)**

<10% of expected taxa.

*represent 95% confidence intervals.*

**Figure 3.**

49%, respectively.

**3.3 Relative extent of stressors**

Nationally, 46% of stream length lost <10% of expected taxa, 13% lost 10–20%, 26% of stream length lost 20–50%, and 15% of stream length lost >50% of expected taxa (**Figure 4**). The Eastern Highlands experienced the greatest loss of expected taxa; 21% of stream length lost >50%, 29% of length lost 20–50% of expected taxa, 10% of length lost 10–20% of taxa, and 40% of stream length lost

*National and regional results from the 2013–2014 National Rivers and Streams Assessment for the benthic macroinvertebrate multimetric index (MMI). Results are presented as the percent of stream length in good, fair and poor conditions, based on the degree of similarity to regionally-defined reference condition. Error bars* 

High levels of several stressors occurred throughout perennial streams and rivers. Excess total phosphorus was the most widespread stressor nationally and within each region. Fifty-eight percent of the river and stream length are marked by high total phosphorus concentrations across the country (**Figure 5A**). The prevalence in the Plains and Lowlands, Eastern Highlands and the West is 51, 73 and

Nutrients (total phosphorus and total nitrogen) were consistently the most extensively occurring stressors with the stream length in poor condition ranging *Rivers and Streams: Upgrading Monitoring of the Nation's Freshwater Resources - Meeting… DOI: http://dx.doi.org/10.5772/intechopen.92823*

#### **Figure 3.**

*Water Quality - Science, Assessments and Policy*

logic alteration is near completion.

extent and risk.

**3. Results**

by the NRSA.

evidence of the need to act.

**3.1 Benthic macroinvertebrate conditions (MMI)**

2008–2009 NRSA are available elsewhere [28, 48].

**2.7 Ranking of stressors: relative extent and relative risk**

philosophy was to understand the most significant stressors first. This information can be used in the process of source tracking and determining probable causes, which are logical future steps for the NRSA and similar national assessments.

and four were related to habitat alterations. The chemical stressors were excess total nitrogen (total N), excess total phosphorus (total P), excess salinity (based on conductivity), and acidification (based on acid neutralizing capacity). Prior 305(b) reports from States or national attention were the basis for these selections. Indicators of habitat alteration have not historically been included in monitoring by most water quality agencies. With a focus on the CWA goals, physical integrity became a needed element within NARS. Four indicators of physical integrity, excess fine sediments, alterations of instream fish habitat, alteration of riparian vegetation structure, and disturbance of the riparian zone are the initial focus. A fifth, hydro-

Eight stressor indicators were selected for reporting. Four stressors were chemical,

An important prerequisite to making policy and management decisions is an understanding of the relative magnitude or importance of potential stressors across a region and the expected benefit of reducing or eliminating that stressor. Both the prevalence (i.e., extent of stream length with high levels of the stressor) and the severity (i.e., impact on biological condition) of each stressor were

considered. The NRSA reports include separate ranking for each of these elements,

Relative extent is a measure of how widespread the problem is…how much of the river and stream length has high levels of that particular stressor. Does high nitrogen occur in few or in many streams and rivers? Are high nitrogen levels geographically isolated or widespread? Relative risk, on the other hand, addresses the severity of the impact of high nitrogen on the biota when it occurs as compared to when nitrogen levels are low. Neither of these measures individually is a good indication that the problem should be addressed. But when combined, they provide powerful

Fish, macroinvertebrates and periphyton samples were all collected during the 2013–2014 stream and river survey. The data were processed and assessed and can be found in the detailed online dashboard and report [47]. Here we present the results for just the macroinvertebrate assemblage as an example of data generated

Nationally, 44% of the perennial stream and river length (hereafter simply referred to as "stream length") was in poor condition, and 26% was in fair condition as measured by the benthic macroinvertebrate MMI relative to the least-disturbed reference condition in each of the nine aggregated ecoregions (**Figure 3**). Based on the MMI, 42% of stream length in the Eastern Highlands, 47% of stream length in the Plains and Lowlands, and 31% of stream length in the West were in poor condition. Detailed examples of results for the nine aggregated ecoregions for the

**120**

*National and regional results from the 2013–2014 National Rivers and Streams Assessment for the benthic macroinvertebrate multimetric index (MMI). Results are presented as the percent of stream length in good, fair and poor conditions, based on the degree of similarity to regionally-defined reference condition. Error bars represent 95% confidence intervals.*

#### **3.2 Benthic macroinvertebrate taxa (O/E index)**

Nationally, 46% of stream length lost <10% of expected taxa, 13% lost 10–20%, 26% of stream length lost 20–50%, and 15% of stream length lost >50% of expected taxa (**Figure 4**). The Eastern Highlands experienced the greatest loss of expected taxa; 21% of stream length lost >50%, 29% of length lost 20–50% of expected taxa, 10% of length lost 10–20% of taxa, and 40% of stream length lost <10% of expected taxa.

#### **3.3 Relative extent of stressors**

High levels of several stressors occurred throughout perennial streams and rivers. Excess total phosphorus was the most widespread stressor nationally and within each region. Fifty-eight percent of the river and stream length are marked by high total phosphorus concentrations across the country (**Figure 5A**). The prevalence in the Plains and Lowlands, Eastern Highlands and the West is 51, 73 and 49%, respectively.

Nutrients (total phosphorus and total nitrogen) were consistently the most extensively occurring stressors with the stream length in poor condition ranging

#### **Figure 4.**

*National and regional results from the 2013–2014 National Rivers and Streams Assessment for the benthic macroinvertebrate observed/expected (O/E) index of taxon loss. Results are presented as the percent of stream length in four categories of taxon loss.*

#### **Figure 5.**

*Relative ranking of stressors nationally and regionally for the 2013–2014 National Rivers and streams assessment. (A) Relative extent is the percent of stream length in poor condition for each of the eight stressors evaluated. (B) Relative risk of observing poor biological condition (based on values of the benthic invertebrate multimetric index [MMI]) given poor stressor conditions relative to observing poor MMI values given good or moderate stressor conditions. (C) Attributable risk is the percent of improvement (i.e., decrease) in stream length in poor biological condition (based on MMI scores) given that a stressor level is modified from poor to good or fair condition. Error bars represent 95% confidence intervals.*

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from about 20% to about 75% across the three major regions (**Figure 5A**). Poor conditions for the four physical habitat indicators were observed in about 20% of stream length nationally, but ranged from 10 to 25% across the three climatic regions. There was much more variability in physical habitat condition at the finer ecoregion scale, with 4 to 40% of stream length in poor condition among the 9 ecoregions, depending on the specific physical habitat indicator and region. Alteration of riparian vegetation cover was the most extensive habitat stressor nationally and in the Eastern Highlands and the Plains and Lowlands regions. High

Almost all stressors evaluated in the NRSA were associated with increased risk for poor macroinvertebrate condition (**Figure 5B**). Nationally, the relative risk values ranged from 1.4–2.0, with only slight or no substantial difference among the stressors nationally. In fact, two of the stressors, acidification and increased salinity,

Relative risk values differed among major NRSA regions (**Figure 5B**). The largest relative risk value (3.9) occurred for total nitrogen in the West, showing that streams with excess total nitrogen were nearly 4 times more likely to have their benthic macroinvertebrate assemblage in poor condition when compared to streams with moderate or low concentrations of total nitrogen. All the stressors posed a risk to macroinvertebrate biological integrity with relative risks values ranging from 1.3

As described above, the use of relative extent and relative risk in combination provides the best assessment of a particular stressor. It provides an estimate of the relative improvement in the biota with the reduction of that stressor (**Figure 5A**–**C**). Rivers and streams are at greatest risk when the stressor is both widespread (large percentage of river and stream length with stressor at excess levels, **Figure 5A**) and presents potentially severe effects (i.e., high relative risk values, **Figure 5B**). Another tool from epidemiology, the concept of attributable risk, was adapted and applied to the data from the Wadeable Streams Assessment [49], and is now part of all of assessments produced from the NRSA surveys. Attributable risk combines relative extent with relative risk to produce a single number that can be used to rank stressors and to inform management decisions by suggesting the level of improvement expected (in terms of the % of stream length in poor biological condition that could be elevated to good condition) if excess levels of a particular stressor are

Nationally, excess total nitrogen and total phosphorus are the stressors whose relative extent (how widespread) and relative risk (severity of impact when excess levels occurred) suggest the largest expected improvement. For each of these nutrients, roughly a 25% improvement (i.e., decrease) in the stream length in poor biological condition is expected if levels of these nutrients are reduced from excess to moderate or low (**Figure 5C**). Excess fine sediments and alteration of the riparian vegetation were the habitat stressors that would produce the largest expected improvement in stream and river biological condition (a 16 and 12% improvement, respectively). Salinity occurs in excess levels in a very low percentage of stream length (**Figure 5A**) and despite high relative risk (**Figure 5B**), this stressor has a very small attributable risk. Thus, excess salinity might be considered a local issue

levels of excess fine sediments were most prevalent in the West.

*DOI: http://dx.doi.org/10.5772/intechopen.92823*

**3.4 Relative risk of stressors**

had among the largest relative risk values.

reduced to moderate or low levels.

to 3.9 nationally and in all three geoclimatic regions.

**3.5 Attributable risk - combining stressor extent and relative risk**

*Rivers and Streams: Upgrading Monitoring of the Nation's Freshwater Resources - Meeting… DOI: http://dx.doi.org/10.5772/intechopen.92823*

from about 20% to about 75% across the three major regions (**Figure 5A**). Poor conditions for the four physical habitat indicators were observed in about 20% of stream length nationally, but ranged from 10 to 25% across the three climatic regions. There was much more variability in physical habitat condition at the finer ecoregion scale, with 4 to 40% of stream length in poor condition among the 9 ecoregions, depending on the specific physical habitat indicator and region. Alteration of riparian vegetation cover was the most extensive habitat stressor nationally and in the Eastern Highlands and the Plains and Lowlands regions. High levels of excess fine sediments were most prevalent in the West.

### **3.4 Relative risk of stressors**

*Water Quality - Science, Assessments and Policy*

**122**

**Figure 5.**

**Figure 4.**

*length in four categories of taxon loss.*

*Relative ranking of stressors nationally and regionally for the 2013–2014 National Rivers and streams assessment. (A) Relative extent is the percent of stream length in poor condition for each of the eight stressors evaluated. (B) Relative risk of observing poor biological condition (based on values of the benthic invertebrate multimetric index [MMI]) given poor stressor conditions relative to observing poor MMI values given good or moderate stressor conditions. (C) Attributable risk is the percent of improvement (i.e., decrease) in stream length in poor biological condition (based on MMI scores) given that a stressor level is modified from poor to* 

*National and regional results from the 2013–2014 National Rivers and Streams Assessment for the benthic macroinvertebrate observed/expected (O/E) index of taxon loss. Results are presented as the percent of stream* 

*good or fair condition. Error bars represent 95% confidence intervals.*

Almost all stressors evaluated in the NRSA were associated with increased risk for poor macroinvertebrate condition (**Figure 5B**). Nationally, the relative risk values ranged from 1.4–2.0, with only slight or no substantial difference among the stressors nationally. In fact, two of the stressors, acidification and increased salinity, had among the largest relative risk values.

Relative risk values differed among major NRSA regions (**Figure 5B**). The largest relative risk value (3.9) occurred for total nitrogen in the West, showing that streams with excess total nitrogen were nearly 4 times more likely to have their benthic macroinvertebrate assemblage in poor condition when compared to streams with moderate or low concentrations of total nitrogen. All the stressors posed a risk to macroinvertebrate biological integrity with relative risks values ranging from 1.3 to 3.9 nationally and in all three geoclimatic regions.

#### **3.5 Attributable risk - combining stressor extent and relative risk**

As described above, the use of relative extent and relative risk in combination provides the best assessment of a particular stressor. It provides an estimate of the relative improvement in the biota with the reduction of that stressor (**Figure 5A**–**C**). Rivers and streams are at greatest risk when the stressor is both widespread (large percentage of river and stream length with stressor at excess levels, **Figure 5A**) and presents potentially severe effects (i.e., high relative risk values, **Figure 5B**). Another tool from epidemiology, the concept of attributable risk, was adapted and applied to the data from the Wadeable Streams Assessment [49], and is now part of all of assessments produced from the NRSA surveys. Attributable risk combines relative extent with relative risk to produce a single number that can be used to rank stressors and to inform management decisions by suggesting the level of improvement expected (in terms of the % of stream length in poor biological condition that could be elevated to good condition) if excess levels of a particular stressor are reduced to moderate or low levels.

Nationally, excess total nitrogen and total phosphorus are the stressors whose relative extent (how widespread) and relative risk (severity of impact when excess levels occurred) suggest the largest expected improvement. For each of these nutrients, roughly a 25% improvement (i.e., decrease) in the stream length in poor biological condition is expected if levels of these nutrients are reduced from excess to moderate or low (**Figure 5C**). Excess fine sediments and alteration of the riparian vegetation were the habitat stressors that would produce the largest expected improvement in stream and river biological condition (a 16 and 12% improvement, respectively). Salinity occurs in excess levels in a very low percentage of stream length (**Figure 5A**) and despite high relative risk (**Figure 5B**), this stressor has a very small attributable risk. Thus, excess salinity might be considered a local issue

requiring a local targeted management approach, severe when it occurs, yet not of significance at a national or regional scale.
