Application of the Indicators of Hydrological Alteration method to the Mkomazi River, KwaZulu-Natal, South Africa

Abstract

Hydrological regimes play a major role in structuring the biotic diversity within river ecosystems and hydrological variation is recognised as a primary driving force within those ecosystems. The US Nature Conservancy developed a method known as the Indicators of Hydrological Alteration, IHA (Richter et al. 1996(Richter et al. , 1997(Richter et al. , 1998, for assessing the degree of hydrological alteration attributable to human induced changes within an ecosystem. The method is based on the statistical analyses of 33 hydrological parameters representing five streamflow characteristics that can be attributed to playing major roles in determining the nature of aquatic and riparian ecosystems (Richter et al. 1996(Richter et al. , 1997(Richter et al. , 1998. The Range of Variability Approach, RVA, is an application of the IHA, incorporating the concepts of hydrological variability and river ecosystem integrity, and was developed to enable river managers to define and adopt preliminary flow management targets before conclusive, long-term ecosystem research results are available. This paper presents an application of the RVA to simulated streamflows at two of the four Instream Flow Requirements (IFR) Sites on the Mkomazi River in KwaZulu-Natal, South Africa, in order to assess the extent of alteration caused by human induced changes to the hydrological regime. The assessment was achieved by comparing the range of variation of the hydrological regime simulated under natural catchment conditions (pre-impact) with the variation resulting from catchment development (post-impact). The 25 th and 75 th percentile values of each of the 33 parameters were selected as the lower and upper thresholds within which streamflow management targets could be set. By setting preliminary streamflow management thresholds that can be modified and refined when ecological data and information become available, the RVA incorporates flexibility and adaptability.

Size‐dependent survival of brook trout Salvelinus fontinalis in summer: effects of water temperature and stream flow

“…F B = 1 if big flood event occurs during certain sampling interval, F B = 0 otherwise. In addition, some of the indicators of hydrological alteration (IHA) variables (Richter et al , 1998; Taylor et al , 2003) were considered but the present variables were found to have better explanatory power (unpubl. data).…”

Zooplankton Community Responses in a Perturbed Tropical Stream in the Niger Delta, Nigeria~!2009-07-22~!2009-10-22~!2010-04-09~!

“…This high pollution status threatens and, in many cases, has already altered the ecological balance of most rivers in Nigeria [1][2][3]. Zooplankters offer several advantages as indicators of environmental quality in both lakes and rivers: as a group, they have worldwide distribution and the species composition and community structure are sensitive to changes in environmental conditions, nutrient enrichment [4][5][6] and different levels of pollution [7][8][9]. Zooplankton play an important ecological role in lakes and rivers, feeding on non-living organic matter, phytoplankton and bacteria, and in turn being eaten by secondary consumers such as fish [10].…”

“…Zooplankton play an important ecological role in lakes and rivers, feeding on non-living organic matter, phytoplankton and bacteria, and in turn being eaten by secondary consumers such as fish [10]. The physico-chemical parameters of an aquatic ecosystem are very important in assessing the composition of any aquatic biota and also their sensitivity to pollution [5,10,11]. Therefore, a major interest in zooplankton investigation is to understand environmental factors that influence their diversity [12].…”

Drivers of spatial and temporal variability of streamflow in the Incomati River basin

“…33 selected gauges from the Incomati basin were analysed with this method using daily flow data. Many studies successfully applied the methodology of Indicators of Hydrologic Alteration, in order to assess impacts on streamflow caused by anthropogenic drivers (Maingi and Marsh, 2002;Taylor et al, 2003;Mathews and Richter, 2007;De Winnaar and Jewitt, 2010;Masih et al, 2011). In the case of the present study, the indicators of the magnitude of monthly flow, the magnitude and duration of extreme flow, as well as timing, were analysed for the period 1970-2011, to assess whether consistent trends of increase or decrease of the hydrological indicators were present.…”