Developing reference criteria for the ecological status of West African rivers
Environ Monit Assess
Developing reference criteria for the ecological status of West African rivers
Idrissa Kaboré 0 2
O. Moog 0 2
A. Ouéda 0 2
J. Sendzimir 0 2
R. Ouédraogo 0 2
W. Guenda 0 2
A. H. Melcher 0 2
0 J. Sendzimir International Institute for Applied Systems Analysis (IIASA) , Laxenburg , Austria
1 Centre for Development Research, Institute of Hydrobiology and Aquatic Ecosystem Management, BOKU University of Natural Resources and Life Sciences , Vienna , Austria
2 R. Ouédraogo Ministère de la Recherche Scientifique et de l'Innovation, Institut de l' Environnement et de Recherches Agricoles (INERA) , Ouagadougou , Burkina Faso
Awareness of sustainable management of water and its biological resources is rising in West Africa, but application of effective tools for biomonitoring and detecting habitats at risk in aquatic ecosystems is limited. In this study, we provide key environmental descriptors to characterize reference sites by applying the following Ba priori criteria^ (physical and chemical, hydromorphological, and land use parameters) by exploring their potential to determine suitable reference sites. Using data collected from 44 sites, we identified 37 criteria that reliably identify reference conditions in semi-arid rivers by reflecting the impacts of multiple pressures ranging from low to very high intensity of human uses and impairments. We integrated all these impacts in an overall pressures index, which showed that protected areas can reasonably be considered as credible reference sites as far as they show low overall impact levels from cumulative pressures. We recommend that development of bio-indicator standards should be based on the collection and integration of all the available information, especially quantitative, spatially-explicit data, from benthic macroinvertebrates and fish. Rigorous standardization of bio-indicator protocols will make them more easily applicable for management and conservation of aquatic ecosystem resources in semi-arid zones of Africa.
Multiple pressures; Reference conditions; Arid; Rivers
Introduction
In Burkina Faso (BF), high water demand due to a high
population growth rate and low management capacity
has led to overuse of surface water. Two major factors
affecting BF river systems are urbanization and
agriculture activities
(Ouédraogo 2010; Melcher et al. 2012;
Kaboré et al. 2015)
, and several mining activities. Their
combination lowers water quality by depositing
untreated domestic waste in the rivers and their tributary creeks
and channels. In addition, BF river flow regimes have
been altered as increasing water demand required dam
construction on rivers to establish a water storage
network of reservoirs. These alterations to Burkina Faso
catchments and their channels have resulted in new
water flow and sediment regimes in the rivers and hence
a net change in their ecological status. Despite the
pressing need to preserve these water resources for
human uses and to maintain the biotic integrity of
riverine ecosystems, few studies
(Guenda 1996; Sanogo
et al. 2014)
have addressed the ecological status of
aquatic ecosystems in Burkina Faso or the means to
assess that status, e.g., biomonitoring.
The purpose of biomonitoring in aquatic ecosystems
is to evaluate the effect of human activities on biota and
the resources they depend on. Several techniques are
used in aquatic ecosystem biomonitoring programs,
including saprobic techniques
(from Kolkwitz and
Marsson 1902 to Rolauffs et al. 2004)
, diversity
indices (Metcalfe 1989), biotic indices and scores
(Armitage et al. 1983; Dickens and Graham 2002;
Ofenboeck et al. 2010; Kaaya et al. 2015)
multivariate
techniques
(Norris and Georges 1993; Kokes et al.
2006)
, and multimetric indices
(Barbour et al. 1995;
Hering et al. 2006)
.
One important component of the biological
assessment of stream conditions using macroinvertebrate
communities is an evaluation of the direct or indirect
effects of human activities or disturbances
(Hering
et al. 2006; Moog et al. 2008)
.
The reference condition approach is one of the most
effective techniques for biomonitoring and assessing the
ecological status of aquatic ecosystems. Thus, every
bioassessment approach requires the identification of
reference sites and reference conditions
(Wright et al.
1984; Resh 1995)
. According to Barbour et al. (1996),
Roux et al. (1999)
,
Ollis et al. (2006)
, and
Stoddard et al.
(2006)
, the reference condition (1) is defined as Bthe
condition that is representative of a group of minimally
disturbed sites organized by selected physical, chemical,
and biological characteristics^ and (2) represents the
expected condition for a particular biotic component
and acts as a benchmark against which data from a
monitoring site is compared. With the reference
condition approach, the biological community of a potentially
stressed waterbody is compared with that of relatively
undisturbed reference sites that have similar (...truncated)