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Getting Started with Nutrient Criteria

Getting Started with Nutrient Criteria. Brian Haggard and Thad Scott Arkansas Water Resources Center University of Arkansas System Division of Agriculture. Why do nutrients matter?. Dodds et al 2008 Env . Sci. & Technol. Aesthetic perception. Macrophyte growth.

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Getting Started with Nutrient Criteria

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  1. Getting Started with Nutrient Criteria Brian Haggard and Thad Scott Arkansas Water Resources Center University of Arkansas System Division of Agriculture

  2. Why do nutrients matter? Dodds et al 2008 Env. Sci. & Technol. Aesthetic perception Macrophyte growth Commercial fisheries/aquaculture Algal blooms Property values Biodiversity Angling Heterogeneity of food quality for consumers Recreation Algal taste and odor Nutrients Algal toxins Fish kills O2 Water clarity Water quality Livestock and human health

  3. Essentially, increased nutrients negatively impact water quality and use. Aesthetic perception Macrophyte growth Commercial fisheries/aquaculture Algal taste and odor Algal toxins Water clarity O2 Fish kills Livestock and human health Water quality Recreation Angling Biodiversity Property values Nutrients

  4. So, how much is too much? Nutrient criteria establish how much is too much. Aesthetic perception Algal taste and odor Algal toxins Water clarity O2 Fish kills A little nutrients A lot of nutrients

  5. How are criteria developed? EPA recommends three approaches for setting nutrient criteria: • Frequency Distributions - Select criteria based on the median of a percent of the data • Literature Review - Investigate nutrient threshold studies or criteria set by other states, tribes, etc. • Stressor - Response Relationships - Select criteria based upon how biological data respond to stressors, i.e. nutrient data

  6. Frequency Distribution: 75% of Data EPA guidance suggests this for data from streams that represent natural [physical, chemical and biological] conditions… Criteria 75% of the data 25% of the data Low High Nutrient Concentration

  7. Frequency Distribution: 25% of Data EPA guidance suggests this for data from all streams within a region… Criteria 25% of the data 75% of the data Low High Nutrient Concentration

  8. This is meant to provide a possible range of reference conditions… It is assumed that these percentiles of the data will have similar values… however, this is not always the case. The percentiles of nutrient concentrations should be used in conjunction with additional info to establish criteria… 75% 25% All Streams Natural Conditions Low High Nutrient Concentration

  9. Let’s look at some data from Texas… There is more variability in phosphorus concentrations in streams when we consider higher percentiles. Little variation in P concentration 25%

  10. Let’s look at some data from Texas… Again, we see greater variability when we consider higher percentiles. Greater variation in N concentration 75% Little variation in N concentration 25%

  11. Now let’s look at the data by basin… Basins There are more basins in Texas than Level III Ecoregions. A lot of variation 75% Some variation at 25%

  12. Now let’s look at the data by basin… Basins We still see variation between basins when we consider higher percentiles. Greatest variation in N concentration 75% More variation in N concentration 50% Little variation in N concentration 25%

  13. What kind of data are used to look at these relationships? • We used data collected from many streams across Texas from 2000-2010. • Last year, we used all available data. • This year, we re-analyzed the data using only some of the data. • For example, we did not use data that were collected under biased flow conditions, for special studies, or that were collected by volunteers; we used data that were quality assured. UA Division of Agriculture Arkansas Water Resources Center

  14. But, we didn’t see much difference in the median concentrations… • The median concentrations were similar when we looked at all the data compared to a sub-set. UA Division of Agriculture Arkansas Water Resources Center

  15. We have to consider other stats when setting criteria… • We shouldn’t just look at these distributions to develop nutrient criteria. • We should also consider criteria reported in the literature that has been developed for other states, ecoregions and watersheds. • We reviewed 124 papers on nutrient criteria and studies applicable to Texas. • And, we should consider relationships between stressors and responses---that’s what we’ll talk about next. UA Division of Agriculture Arkansas Water Resources Center

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