Survey Designs and Field Data Collection

Survey designs

Appropriate sample designs depend on specific research or management questions and the scale that you are seeking to make inference to. We detail three common sampling designs here: 

  1. Single point in time sampling at a site and comparison to reference site populations to determine conditions. In this sampling design, variation across sites is considered to be a surrogate for variation through time at a site and so one point in time assessment is considered adequate for baseline assessments (Stewart-Oaten and Bence 2001).
  2. Before after control impact (BACI) designs are frequently used to assess local scale questions about effectiveness of specific management actions. 
  3. Spatially balanced probabilistic designs (e.g. Generalized Random Tessellation Stratified (GRTS)) are frequently used to address regional scale questions such as condition and trend of all streams within a given field office or management unit (Olsen et al. 2009, 2012). 

In any study design it is important to consider at what scale are samples independent of one another and pseudo-replication and spatial auto correlation are particularly of concern in stream systems due to their high connectivity. However, there is not general agreement on an approach to ensure statistical independence of stream reaches and independence will vary by indicator. For example, water quality indicators will be more correlated upstream and downstream than bank stability. However, many rapid-assessment protocols scale size of reach sampled with stream size and implement measurements along 11-21 transects across >110 m long reaches.

Typical reach setup with 11 main transects (A-K; black lines) and 10 intermediate transects (gray lines) oriented perpendicular to the thalweg. Reach lengths are equal to 20x bankfull width or a minimum of 150 m

Comparability and precision of field methods

Field methods for macroinvertebrate sampling for bioassessments have largely been standardized across many monitoring programs, and we recommend two primary methods: a targeted-riffle approach or a reachwide transect based approach (Rehn et al. 2007). These approaches sample standardized areas rather than standardizing sampling by time or proportional habitat-based approaches. Standardizing by area is important for reliably assessing species richness (Vinson and Hawkins 1996).

subser sampling

Likewise, water quality field measurements are relatively straightforward and either use in-situ sonde based measurements, grab samples that are preserved in some manner, or in-situ data loggers.

YSI meter

There is more variability in physical habitat methods used across monitoring programs and protocols and indicators vary in repeatability and ability to detect change over time (Roper et al. 2003, 2010, Al-Chokhachy et al. 2011).

Literature Cited

  • Al-Chokhachy, R., B. B. Roper, E. K. Archer, and S. Miller. 2011. Quantifying the Extent of and Factors Associated with the Temporal Variability of Physical Stream Habitat in Headwater Streams in the Interior Columbia River Basin. Transactions of the American Fisheries Society 140:399–414.
  • Olsen, A. R., T. M. Kincaid, and Q. Payton. 2012. Spatially balanced survey designs for natural resources. Pages 126–150 in R. A. Gitzen, J. J. Millspaugh, A. B. Cooper, and D. S. Licht (editors). Design and Analysis of Long-term Ecological Monitoring Studies. Cambridge University Press, Cambridge.
  • Olsen, A. R., B. D. Snyder, L. L. Stahl, and J. L. Pitt. 2009. Survey design for lakes and reservoirs in the United States to assess contaminants in fish tissue. Environmental Monitoring and Assessment 150:91–100.
  • Rehn, A. C., P. R. Ode, and C. P. Hawkins. 2007. Comparisons of targeted-riffle and reach-wide benthic macroinvertebrate samples: Implications for data sharing in stream-condition assessments. Journal of the North American Benthological Society 26:332–348.
  • Roper, B. B., J. M. Buffington, S. Bennett, S. H. Lanigan, E. Archer, S. T. Downie, J. Faustini, T. W. Hillman, S. Hubler, K. Jones, C. Jordan, P. R. Kaufmann, G. Merritt, C. Moyer, and A. Pleus. 2010. A Comparison of the Performance and Compatibility of Protocols Used by Seven Monitoring Groups to Measure Stream Habitat in the Pacific Northwest. North American Journal of Fisheries Management 30:565–587.
  • Roper, B. B., J. L. Kershner, E. Archer, R. Henderson, and N. Bouwes. 2003. An evaluation of physical stream habitat attributes used to monitor streams. Journal of the American Water Resources Association 38:1637–1646.
  • Stewart-Oaten, A., and J.R. Bence. 2001. Temporal and spatial variation in environmental impact assessment. Ecological Monographs 71:305-339.
  • Vinson, M. R., and C. P. Hawkins. 1996. Effects of Sampling Area and Subsampling Procedure on Comparisons of Taxa Richness among Streams. Journal of the North American Benthological Society 15:392–399.