The challenge of monitoring impacts of water abstraction on macroinvertebrate assemblages in unregulated streams

Abstract

Monitoring of the ecological impacts of water abstraction from unregulated streams in the state of New South Wales (NSW), Australia, is challenging because water is abstracted by thousands of geographically dispersed users who pump intermittently according to temporally varying needs and the limitations imposed by licences and access rules. Detailed, quantitative monitoring methods are too costly for widespread routine application because of the size of the state (801 000 km 2 ) and the large number of streams affected by abstraction. We therefore tested the possibility of detecting abstraction impacts on aquatic macroinvertebrates with rapid biological assessment (RBA) methods similar to those that are routinely used for biological monitoring of Australian rivers. We sampled 85 sites on unregulated streams in north-eastern NSW during a period of prolonged and recurring drought, 54 of which were designated as reference sites with respect to water abstraction because upstream entitlement for abstraction was less than 1% of their mean annual flow (MAF). The remaining, non-reference sites had an average of 4% of MAF licensed for upstream abstraction (range 1-20%). Sweep and kick samples were collected at each site in two seasons, and invertebrates were picked for 30 min per sample and analysed at genus level. We found a small but statistically significant overall difference in macroinvertebrate assemblages between the reference and non-reference sites, but the amount of upstream entitlement did not affect the degree to which assemblages at individual sites deviated from site-specific reference conditions. We attribute the absence of evident impact mainly to the low proportions of streamflow abstracted, but limitations of RBA methods may also be a factor. We recommend a risk-based approach to future monitoring whereby effort is focussed on those streams where a high proportion of flow is abstracted.

Macroinvertebrate traits distinguish unregulated rivers subject to water abstraction

“…This situation occurred in 30% of cases for riffles and 22% for edges, substantially above the 10% expected by chance if all test samples were actually in reference condition (reference condition for our purposes was an absence of licensed upstream abstraction rather than minimal disturbance by all human activities). This result contrasts with a previous study by Chessman et al (2011), who found no evidence of effect from water abstraction on macroinvertebrate assemblages in unregulated rivers of northeastern NSW using similar predictive modeling. This difference may be related to the much-smaller geographic area and number of sites considered by Chessman et al (2011) than in our study and the apparently low level of abstraction upstream of many of their test sites.…”

“…This result contrasts with a previous study by Chessman et al (2011), who found no evidence of effect from water abstraction on macroinvertebrate assemblages in unregulated rivers of northeastern NSW using similar predictive modeling. This difference may be related to the much-smaller geographic area and number of sites considered by Chessman et al (2011) than in our study and the apparently low level of abstraction upstream of many of their test sites.…”

Bringing groundwater models to LIFE: a new way to assess water resource management options

“…The response of the individual macro-invertebrate taxa to the effect of abstraction was consistent with the RIVPACS-based model, giving confidence to the methods presented here (Bradley et al 2013). Furthermore, the results presented in Bradley et al (2013) were consistent with other studies on the impacts of abstraction on macroinvertebrates that showed that impacts were most obvious with substantial dewatering (Armitage and Petts 1992, Bickerton et al 1993, Castella et al 1995, Chessman et al 2011.…”

Unravelling the joint effects of flow regime, climatic variability and dispersal mode on beta diversity of riverine communities

“…However, analysis of presenceabsence and abundance data may provide different insights into the effects of flow regime and climatic variation on regional biodiversity (e.g. Clarke et al, 2010;Chessman, Royal & Muschal, 2011;Huttunen et al, 2014). The inclusion of abundance data allows for effects on community structure to be assessed as well as effects on community composition (Anderson et al, 2011).…”