FAQ - Frequently Asked Questions

Q: Is the method applied in ASSESS-HKH also applicable to assess the quality of ground water?

A: No. ASSESS-HKH aims at assessing the surface water quality of streams and rivers in the Hindu Kush-Himalayan region. The sampling design is not suited for groundwater assessment. Groundwater assessment is usually done by means of chemical and physical analysis, in particular where it is used for drinking water supply. The reason is that many specific pollutants and chemical substances are known to be harmful to human health, even in very low concentrations, whereas bio-indicators for most of these substances lack at all.


Q: How are benthic macroinvertebrates linked to water quality assessment?

A: Water quality deterioration has manifold impacts on aquatic organisms. Toxic substances may directly influence the fauna and flora and reduce their number and diversity. Organic pollution originating from public waste water or industrial effluents dramatically increases bacterial growth and consequently bacteria’s oxygen demand. The rapid oxygen depletion causes a quick and severe depletion of benthic macroinvertebrates and fish. Organisms adopted to high current velocities and oxygen contents will vanish first, such as stoneflies and many mayflies. Acid rain and other acid substances may reduce the pH-value of streams and acts upon fish gills, which often causes fish kills.


Q: How can students or local residents apply for a training in ASSESS-HKH methods?

A: Interested people should apply for a training at the ASSESS-HKH partner institutes in their country. Training courses may be frequently offered by partner institutes. Contact addresses of the partner institutes are available on this website.

(back to top)


Q: Which species are to be considered for distinguishing different water quality classes?

A: As the fauna within the Hindu Kush Himalayan region may show regional differences, the answer to this question is difficult if given addressing the species level. Therefore, the answer is given here with respect to higher taxonomical levels (e. g., genus, family, order). High-quality sites are usually colonised by a species-rich and abundant community including a variety of stoneflies, mayflies, and caddisflies. In contrast, severe deterioration is often indicated by the dominance of non-biting midges and worms, whereas the former taxa are sparse or may even lack. As deterioration is often connected to flow reduction, organisms that prefer lentic conditions and fine sediments are frequent and abundant at degraded sites. The explicit nomination of intermediate taxa capable of indicating moderate quality is difficult.


Q: What is the impact of plant leaves?

A: At reference sites in (leafed) forested ecoregions, plant leaves frequently occur in streams and rivers. They play an important role within aquatic ecosystems. Many macroinvertebrates known as “shredders” feed on leaves and other organic plant material. Moreover, shredders produce fine organic matter by breaking up and ingesting coarse particulate plant material. The fine material, in turn, provides food for filterers, gatherers and collectors, i. e. macroinvertebrates that feed on fine particulate organic matter (FPOM). Therefore, plant leaves and other plant material belong to each aquatic ecosystems in naturally forested areas.

(back to top)


Q: Do macroinvertebrate bio-indicators differ between geographical regions?

A: Although not generally valid, the answer must be yes. If mountain and lowland regions are compared, a lot of macroinvertebrate groups are known to be limited to either one or the other ecoregion. It is obvious that streams in both ecoregions differ in terms of slope and, thus, mean current velocity. Other differences are, for example, substrate particle size, mean annual temperature or the hydrologic regime. Hence, natural mountain streams frequently inhabit those species adapted to lotic flow conditions, low water temperatures, and coarse substrates. Consequently, the impact of oxygen depletion due to organic pollution is likely to be stronger in lowland streams, where the oxygen enrichment by turbulent flow is much higher. As the macroinvertebrate community usually changes between ecoregions or, rather, bioregions, it is likely that indicator taxa also change.


Q: Do macroinvertebrates adapt to pollution, thus loosing their indication value?

A: No. Macroinvertebrates do not adapt to pollution. If they would, they were definitely not suited to be indicators. However, one must distinguish between sensitive and tolerant indicators. In case of organic pollution, sensitive indicators usually lack and show impact just by not being present. Tolerant indicators usually are adapted to pollution by means of physical particularities, such as extra gills or the capability to breath air. Although they may also be present at reference sites, their competitive value is highest at polluted sites, thus, leading to individual-rich communities. Therefore, bio-indication should always refer to both presence and abundance of taxa.

(back to top)


Q: What is self-purification?

A: Self-purification is the ability of a stream to reduce the organic pollution within a stream section by natural processes. A stream’s ability to self-purify strongly depends on the hydrological and morphological deterioration. Good hydromorphological conditions promote a rapid degradation of organic material by in-stream bacteria and ensure a steady oxygen supply by turbulence. Within several hundreds of meters up to some kilometres pollutants can be metabolised and may serve as food source for bacteria-feeding organisms. Released nutrients may be immediately immobilised by incorporation into aquatic plants. Organic pollution diminishes downstream.


Q: Is reduction (presence of iron sulphide layers) always related to poor or bad water quality?

A: No. Reduction may also occur at sections with a good water quality, but with large patches of fine sediments (silt, clay) on the stream bottom. By clogging the interstices of coarser substrates, the fine particles inhibit the water flow within the stream bottom and, thus, the oxygen supply. Consequently, reduction occurs where the sediment is covered, for example, under stones or pieces of large wood.

(back to top)


Q: Is there interaction between stressors?

A: Yes. The impact of organic pollution on aquatic animals strongly depends on the hydrological and morphological conditions of the polluted stream section. Damming an the lack of shading may lead to higher water temperatures and reduce the aeration of water. Nutrient enrichment promotes aquatic macrophyte and algal growth that is quicker and more intensive in dammed and unshaded stream sections. Consequently, the impact on fertilizers on the water quality is stronger in dammed sections. The following decomposition of dead plant material may cause oxygen depletion whose negative impact is stronger in dammed sections and stagnant water bodies.


Q: What should be done for the conservation of rivers?

A: First, river conservation needs an understanding of the function of the river ecosystem that includes both the river channel and the riparian (floodplain) areas. There is a strong need to know, how river organisms and their habitats are related before one can derive actions to preserve or restore river ecosystems. Moreover, river restoration may address various issues. For drinking water supply, water quality and quantity are important issues, whereas the function of river organisms is additionally depending on habitat quality. With other words: River health addresses both water quality and the integrity of structures that contain and transport the water.

(back to top)


Q: Which water is more safe for drinking: Groundwater or surface water?

A: The answer can’t be given generally. In many countries, groundwater is used for drinking water supply, as it often provides extremely clear and clean water. No or only minor treatment is necessary to make it drinkable for humans. This particularly applies to mountain areas, where even surface waters like brooks and springs bear drinkable water. However, the case is completely different in Bangladesh, where sediments are loaded with arsenic in large areas and, therefore, the groundwater is also contaminated with arsenic. Thus, the water quality depends on the quality of the sediment layers that store the water.


Q: How is water quality assessment developed?

A: Water quality assessment can be distinguished into 1) chemical analysis and 2) bio-indication. Regular and frequent chemical analysis is necessary to ensure a safe drinking water supply for humans. It aims, for example, at the detection of E-coli bacteria, plant nutrient concentrations that may be harmful to humans, or toxic substances released from industries. As chemical analysis always represents a spot measure, water quality monitoring must be short-termed. Bio-indication, in contrast aims at indicating the negative impact of, for example, organic pollution through waste water on the river organisms. For example, sensitive insect larvae rapidly vanish, where pollution occurs. Other groups of organisms, such as non-biting midges and worms, are less sensitive to pollution and increase in density, where pollution occurs. As the life cycle of those organisms ranges from several weeks to month or even years, bio-indication is capable of integrating impact over long periods. Thus, relatively long-term measures are sufficient, for example three to four times a year in case of indicating organic pollution with benthic macroinvertebrates.

(back to top)