Ecological Indicators
Certain plants and animals can be used to identify the nature and extent of groundwater-surface water interaction. The most common ecological indicators are aquatic plants, phreatophytes and hyporheic biota.
Aquatic plants can be indicators of groundwater discharge. For example, cattail plants have been used as indicators of fresh groundwater input to saline prairie lakes in North Dakota (Swanson et al, 1984). Lodge et al (1989) indicated that submerged aquatic plant biomass was enhanced where groundwater inflow velocity was greater. In a desert stream setting, algae abundances in streambed sediments recovered more rapidly from flash flooding in areas with upward movement of groundwater (Valett et al, 1994). This was attributed to the groundwater providing a source of nutrients to the algae. Mats of green algae and stalked diatoms also coincide with discharge of nutrient-rich groundwater in the generally unproductive Flathead River in Montana (Ward, 1989). Klijn and Witte (1999) discussed the relationship of plants to groundwater flow systems. Groundwater discharge may favour the growth of particular aquatic plants. The predominance of acid-tolerant species such as water lilies can indicate significant discharge of acidic groundwater. Phreatophytes are deep-rooted plants that can access the watertable. Upland phreatophytic plants near a surface water body can indicate the presence of groundwater at shallow depths.
The hyporheic zone is the portion of the stream bed characterised by the mixing of groundwater and surface water. It can be a zone of intense biogeochemical activity and assessing the extent and composition of hyporheic biota can indicate the nature of groundwater-surface water interaction. This includes mapping the distribution of organisms that only temporarily migrate into the sediment from the stream floor such as insect larvae, compared with organisms that are permanent inhabitants of the substrate, such as choronimids and amphipods (Ward & Stanford, 1989). For example, the oligchaete worm Phallodrilus sp can be a useful indicator of groundwater exchange (Lafont et al, 1992). Ostracods are especially useful in assessing past groundwater and surface water relationships because they have specific tolerances to water temperature and chemistry.
Advantages
- readily incorporated at the basic level into field work program with no additional costs;
- useful as a reconnaissance tool to target sites of groundwater discharge; and
- monitoring of ecological indicators may be useful in understanding seasonal changes in seepage flux Such monitoring is important in the evaluation and management of groundwater dependent ecosystems.
Disadvantages
- dependent on observer's expertise in biological identification;
- more detailed studies, such as hyporheic zone investigations require more time, resources and expertise; and
- tends to show where groundwater seepage occurs but is limited in providing quantitative information on seepage flux.
Data Availability
Further Information
Groundwater dependent ecosystems
Riverine ecosystems
Coastal and marine ecosystems
Relevant links
US Environmental Protection Agency Biological indicators of groundwater and surface water interaction
References
Klijn, F and Witte, JP. 1999. Eco-hydrology: groundwater flow and site factors in plant ecology. Hydrogeology Journal. 7, 65-77.
LaFont MA, Durbec A and Ille C, 1992. Oligochaete worms as biological describers of the interactions between surface and groundwaters: a first synthesis. Regulated Rivers: Research and Management 7, 65-73.
Lodge, DM, Krabbenhoft, DP and Striegl, RG. 1989. A positive relationship between groundwater velocity and submerged macrophyte biomass in Sparling Lake, Wisconsin. Limnology and Oceanography. 34, 235-239.
Swanson, GA, Adomaitis, VA, Lee, FB, Serie, JR Shoessmith, JA. 1984. Limnological conditions influencing duckling use of saline lakes in south-central North Dakota. Journal of Wildlife Management. 48, 340-349.
Valett HM, Fisher SG, Grimm NP, Camill P, 1994. Vertical hydrologic exchange and ecological stability of a desert stream ecosystem. Ecology 75(2): 548-560.
Ward JV, 1989. The four-dimensional nature of lotic ecosystems. Journal of the North American Benthological Society 8, 2-8.Ward JV and Stanford JA, 1989. Groundwater animals of alluvial river systems: a potential management tool. In: Grigg NS (ed) Proceedings of the Colorado Water Engineering and Management Conference, Colorado Water Resources Research Institute, Fort Collins, Colorado.