Demystifying River Health-2
This article is in two parts. Part I was about a new name and Part II suggests a way forward.
It is more in nature of loud thinking and is an expression of a personal discomfort with a ‘missing’ terminology with respect to ‘streams’ against few parallels including that with humans and the latter’s unscientific propensity to view a stream as being little more than a carrier of utilizable water.
This is primarily to stir ‘thinking’ and ‘debate’. Comments are most welcome. Terms ‘river’ and ‘stream’ have been used here interchangeably.
When shall we know that a stream is ‘unwell’?
Us humans can ‘feel’ sickness and speak about it.
But a stream if it has a language we are unaware of it and hence in sickness even if it screams it could go unheard, unless we humans begin to suffer as a result.
Interestingly just like us humans where it is often a ‘blood’ test against scientifically determined standards that is carried out for determining the nature and extent of sickness, in case of streams too it is often a water (‘flumen’ in suggested terminology) test against standards that is prescribed. The only difference is that while in case of humans there are large numbers of parameters with respect to different possible diseases which get tested in the case of a stream these are just few namely pH, temperature, DO (Dissolved Oxygen), BOD (Bio chemical Oxygen Demand), Coliform levels and presence/absence of heavy metals. Often just testing for BOD and Coliform levels are thought to be enough.
A framework called as TORT3S is being suggested to identify the state of health of a stream. It starts with the testing of the quality of flumen and goes beyond not unlike in our own (human) case where once blood test report gives abnormal results other diagnostic examination are required to confirm the exact nature of the ailment and possible remedy thereof.
‘Tort’ as we know is a legal term that alludes to injury suffered by a person due to the acts of omission or commission of another person with a consequent legal remedy. Thus the use of a similar term for a stream seems well placed. A stream shall be considered ‘unwell’ when one or more parameter in TORT3S is not conforming to a reference standard.
Expansion of each letter with a presumed human parallel is suggested as:
T-Temperature of flumen (Temperature of human body)
O-Dissolved Oxygen in flumen (Oxygen in human blood & system)
R- State of the Riverbed (State of Organs in Humans)
T- Transparency of flumen (Physical appearance of blood in humans)
S – Speed of flumen (Blood pressure in humans)
S – Suspended particles / salts in solution in flumen (Platelet count, RBC, WBC and salt content etc in human blood)
S – Periodic Submergence by flumen of the stream space (Physical exercise for healthy living by humans)
Let us consider each of them in some detail.
When unwell we often speak of feeling feverish. So high body temperature is an indicator of illness.
Similarly the temperature of Flumen is an important but highly underrated parameter despite it influencing many riverine processes both physical and biological.
But it is important to understand that the normal and desirable temperature of flumen in a stream unlike humans is not and cannot be a single or constant figure throughout the stream. And this brings us to the question of how and wherefrom the temperature in a stream is measured and with what purpose in mind.
“Whether a stream is spring fed or runoff fed is also material with respect to the temperature of the flumen. It is biologically important that a stream which is cool in summer because it is spring fed is warmer in winter than streams fed by runoff”.[i]
Different stretches of the same stream can have different normal temperature as it begins its life from hills (with low ambient temperatures) to plains (with higher ambient temperatures) to delta (with still higher ambient temperatures).
There are both longitudinal and vertical thermal gradient in streams. Diurnal variations where temperatures are highest during afternoon and least in latter half of night are also often experienced.
“One effect of temperature is to alter the viscosity of water (flumen) and this causes silt to sink twice as fast at 23 deg C as it does at 0 deg C. Thus warmer stream carries less silt than colder and flows a little faster”.[ii]
Biological decomposition and hence depletion of dissolved oxygen in flumen is also faster at higher temperatures.
Fish deaths from de-oxygenation of flumen in some streams resulting from sudden release of hot water from industrial sources (often thermal power plants) into streams are commonly reported.
Thus whenever a stream appears in trouble, temperature of its flumen at the point of trouble could be a useful indicator for further investigations.
“Three most important gases in flumen are oxygen, nitrogen and carbon dioxide. Of these nitrogen is not much affected by the biota nor does it enter into complicated relationships with other dissolved substances…. Oxygen and carbon dioxide are usually inversely related to one another because of the photosynthetic and respiratory activities of the biota”.[iii]
Thus it is dissolved oxygen in flumen popularly called DO which is of prime importance. Even common flumen quality tests like BOD (Biochemical Oxygen Demand) and level of Coliform present are an indirect measure of the extent of oxygen present or required in flumen. It may be noted that solubility of gases is dependent on the temperature of the flumen.
Presence/absence of biota in streams (flumenic life) is also a function of the availability of DO in it.
“Many animals, notably trout and many invertebrates can live only in well-aerated water, but it is not the actual amount of dissolved oxygen which matters so much as the percentage saturation”.[iv]
“Living things, and their decay, use up oxygen which can only be replaced from the atmosphere or by the activities of green plants”. (Photosynthesis).[v]
Reason why if there is an overdose of sewage (decomposing organic material) in a stream and little ingress of oxygenated flumen then very soon the entire DO shall get used up and the stream shall turn lifeless. (Yamuna in urban Delhi is an example).
Disagreeable odour (Hydrogen Sulfide gas in particular) emanating from a stream is also an indicator of the depleted state of oxygen in it.
Riverbed including floodplains constitutes the body of a stream.
Under natural conditions riverbed is broadly of two kinds namely ‘eroding’ and ‘depositing’. Additionally most riverbeds exhibit local peculiarities of own. Riverbed is also a function of the stream geometry like sinusoidal (popularly called ‘meander’) or multiple overlapping channels called ‘braiding’.
‘Eroding’ riverbed is characterized by a physical state where bed rock is often visible and is littered with sediments of various shapes and sizes like pebbles, boulders and rocky fragments. These are found mostly in the founding stretches of the streams or in gorges where the impact of gravity on account of sharp gradient is high and resultantly flumen traverses over rapids with the stream transporting huge amounts of eroded material. Such riverbeds provide varied habitats to life forms and are therefore rich in diverse biota especially invertebrates.
On the other hand a ‘depositing’ river bed is the characteristic feature of middle and lower stretches of a river system where moderate gradient results in slow and leisurely movement of flumen giving enough time for sedimentation and the riverbed is marked by deep layers of sand and silt. The habitats here are more uniform and the biota less varied than its eroding counterpart.
In the delta region under the influence of oceanic waxing and waning, the riverbed though depositing in nature gets dominated by silt and clay and the biota gets especially adapted to the unique brackish environment.
“The major controlling factor in the distribution of invertebrates is the nature of the river bed. This is either ‘eroding’ in which event it is rock, stones or gravel, or ‘depositing’, in which event it is silt or mud. The intermediate condition, sand, forms a convenient dividing line as it is not a particularly suitable habitat for animal life…. Superimposed on any of these types of bottom one may find weed beds, which provide a third type of substratum”.
In some streams there are in-stream ponds in the riverbed that find full expression during low flows and are often fed by aquifers. They have important ecological and economic roles to play since they form sites of special biological richness as well as are sources of drinking water and irrigation for local people.
Flumenic and riparian vegetation adapted to stream flows provide stability as well as diversity of habitats to biota found in the riverbeds.
Such natural state of riverbeds can be drastically altered (both upstream and downstream) by manmade engineering structures like dams, hydropower projects, barrages for diversions, bridges, embankments, indiscriminate sand and boulder mining, dumping of wastes and encroachments and land use changes like concrete dominated river front development schemes.
Flumen under most natural conditions is transparent and permits sunlight to penetrate to deeper levels. Since sunlight is essential for photosynthesis, it also impacts the amount and saturation percentage of dissolved oxygen in the flumen.
Transparency of flumen can be adversely impacted by number of natural and manmade reasons. Both dissolved and suspended material can affect the flumen transparency. Change in land use in catchments resulting in greater soil erosion and sediment load in streams is one such important factor.
Similarly polluting sewage and industrial effluents affects it. Effluents from dyeing industries can even color it. Also high sediment load during floods could affect flumen transparency.
Speed of current in stream
“The speed of the current is important, not only directly, but indirectly, as it influences the type of river bed and the amount of silt deposition”.[vii]
Speed of current in a stream varies seasonally and even diurnally and this fact needs to be kept in mind while assessing this parameter as an indicator of health.
“In a swift upland stream the movement and turbulence of the water (flumen) rapidly replenishes any oxygen used and the water (flumen) remains saturated. In a sluggish river, however there is less turbulence and the oxygen is not so readily absorbed from or given up to the air. Thus the amount in solution (flumen) may fall considerably, particularly at night”[viii] (when there is no photosynthetic activity happening).
Speed of current can be altered sometime drastically by manmade structures like anicuts, barrages, dams, bridges and embankments.
Suspended particles and Salts in solution
Both, suspended ‘sediments’ in flumen which are fine (sand, silt and clay) or that standing in the riverbed in bulk (pebbles and boulders) as well as the dissolved ‘salts’ in flumen are integral and essential parts of a stream’s physicality. It also plays an important part in its biology.
Hardness and softness of flumen is a function of the presence/absence of salts like calcium bicarbonate. In chemical terms pH is the measure of acidity (softness) and alkalinity (hardness) of the flumen. “Note that this explanation is a simplification as other factors such as the type of bedrock have an effect on water hardness as well”.[ix]
Hard flumen is utilized by some animals for shells or other skeletal structures, while soft flumen is more fertile for plant growth. Underlying rocks like limestone, slates, shales or granite play key part in the kind of salts available in solution.
Manmade structures like dams, hydropower projects, barrages, anicuts, bridges and embankments as well as mining of riverbed and catchments and land use changes like encroachments and deforestation can affect the size and volume of sediments as well as the composition and amount of salts dissolved in flumen.
Submergence of stream space
A healthy stream shall periodically wet its floodplains in a phenomenon called ‘floods’ to rejuvenate life forms (both plants and animals) present there. It also resultantly replenishes floodplain water bodies which act as nursery to fish and invertebrates and recharges groundwater. Such submergence also brings in and leaves behind fresh silt and sand onto alluvial riverbeds increasing their fertility.
Such submergence is often cyclic with annual, 10 year, 25 year, 50 year, 100 year and 500 year periodicity. Presently 100 year flood limit on either side of the stream bank is presumed to constitute the riverbed limits and is the land that constitutes the stream/river space and which should ideally be free of human interference and presence. Tragically there is no legally mandated demarcation of such flood limits in the Indian context which results in avoidable loss of life and property during floods of people who have ingressed for want of legal prohibitions onto the river space.
Over the years manmade structures like dams have played havoc with this natural periodic waxing and waning of streams affecting riparian life by preventing low level flooding pulses and turning bigger floods into ferocious and devastating events.
It may be noted that a mention of usual and popular presence / absence of ‘biota’ (both plants and animals) as an indicator of stream health has not been highlighted since it is understood that it is not easy to establish reliable baselines or reference standards for the same in terms of either definitive listing or population richness. Moreover the fact remains that the health of biota is a function of most parameters considered within TORT3S.
On the other hand for each parameter considered either for flumen or the stream’s physical state namely Temperature (T), DO (O), Riverbed (R), Transparency (T), Speed (S), Sediments and Salts (S) and Submergence (S) reference standards are easy to establish.
Can the so called E flow restore river’s health?
E flow, often called environmental or ecological flow has been offered as some kind of panacea to improve stream health.
First of all, what flows naturally in a stream in all its natural variations over the seasons and even diurnally is the true E Flow. Secondly there is no single definition of what is the ‘right’ E flow for a stream despite efforts made by several experts over decades.
Yes, we could offer releases as some percentage of virgin flows in streams downstream of interventions like dams and barrage trying to mimic seasonal variations but it shall remain short of the real E flow in a stream. Moreover the nature of flumen to be found in such selective releases shall be vastly different in terms of TORT3S parameters as compared to free flowing streams.
River has immense power of self rejuvenation
While streams can go sick and remain so over a long period of time, they can bounce back to health with relative ease once the factors affecting them are removed. This has been exhibited at many places when either a dam has been removed or with the cessation of the polluting influences.
The only interventions which might take time to subside are those from indiscriminate riverbed mining, encroachments and land use changes or the deforestation and mining in catchment regions.
Humans have that too. Interestingly in case of humans too, it is the human body which heals itself post an illness once a proper diagnoses has been affected. Medicines and other interventions do help but it is the mental resolve and inherent healing power of the human body that actually does the trick.
Manoj Misra (email@example.com)
Manoj Misra, a former forester is the Convener of Yamuna Jiye Abhiyaan.
Original Article Link - https://sandrp.in/2020/09/09/demystifying-river-health-2/
For part I of this article see: https://sandrp.in/2020/09/08/demystifying-river-health-1/
[i] Hynes, H.B.N. (1970). The Ecology of Running Waters. Liverpool University Press. Liverpool. https://books.google.co.in/books/about/The_Ecology_of_Running_Waters.html?id=jRVDAAAAYAAJ&redir_esc=y p. 29
[ii] Ibid., p. 30
[iii] Ibid., p. 40
[iv] Hynes, H.B.N. (1960). The Biology of Polluted Waters. Liverpool University Press. Liverpool. https://onlinelibrary.wiley.com/doi/abs/10.1002/iroh.19610460321 p. 20
[v] Ibid., p. 21
[vi] Ibid., p. 27
[vii] Ibid., p. 19
[viii] Ibid., p. 21