Water can kill

The news of fish deaths in freshwater bodies such as rivers, lakes, ponds is not new to India. Time and again, we continue to hear reports of mass fish deaths from different parts of the country like the Krushnale lake in Panvel, Maharashtra, in Mumbai where hundreds of fish were found dead and floating in the Banganga tank at Walkeshwar or that in a pond in Vishakapatnam, Bengaluru’s Mottanalluru lake, in a pond in Guwahati, or a lake in Kolkata.

This time, a large number of fish have died in the river Mula Mutha and Ramnadi in Pune. What is worrisome is that incidents such as these are getting frequent in a city blessed with beautiful rivers, lakes, streams, ponds which are gradually becoming carriers of filth, thanks to the incessant draining of untreated sewage and harmful wastes into the waters that is smothering aquatic life and putting populations at risk.

On the top of this, the contentious River Front Development project, that includes plans to concretise the banks of the river is moving ahead with its plans to cut trees and rich riparian forests that serve as lifelines for the river.

Citizens and experts fear that this will not only destroy the rich vegetation, but will also further restrict the flow of the river making it unlivable for a range of animals and birds residing in and near the river water, while the basic problem of preventing the poisons and filth from entering into the river remains unaddressed. It is not surprising that Pune is now becoming a hotbed of water borne and vector borne diseases.

Fish deaths are sure indicators of deterioration in the water quality of the river indicating that the water is unsafe for use, consumption and even survival of aquatic animals living in it.

What is water quality?

Good quality water is very important for survival of plants, animals and microorganisms that inhabit freshwater ecosystems, and plays a critical role in maintaining the delicate balance of freshwater ecosystems.

Water quality can be classified into four types—potable water, palatable water, contaminated (polluted) water, and infected water:

• Potable water: is safe to drink, pleasant to taste, and usable for domestic purposes.

• Palatable water: is esthetically pleasing and may have chemicals that do not cause a threat to human health.

• Contaminated (polluted) water: water containing unwanted physical, chemical, biological, or radiological substances, which is unfit for drinking or domestic use.

• Infected water: is contaminated with pathogenic organisms

Read more here

What is water pollution

Water pollution occurs when harmful substances such as chemicals or microorganisms contaminate a stream, river, lake, ocean, aquifer etc degrading water quality and rendering it toxic to humans or the environment.

Surface water is extremely susceptible to pollution due to release of harmful fertiliser and pesticide residues, effluents from industries due to human activities such as agriculture, industrialisation and release of untreated sewage generated in urban areas into water bodies such as rivers and lakes. Groundwater pollution happens due to release of pollutants into the underlying aquifers .

Read more on water pollution here

How do we know that the water is polluted?

Water gets polluted when it falls short of the water quality parameters mentioned below.

Parameters of water quality

There are three types of water quality parameters physical, chemical, and biological

Physical parameters include:

• Turbidity

• Temperature

• Colour

• Taste and odour

• Dissolved Solids

• Electrical conductivity

Chemical parameters:

• pH

• Acidity

• Alkalinity

• Chloride

• Chorine residual

• Sulphates

• Nitrogen

• Fluoride

• Iron and manganese

• Copper and zinc

• Hardness

• Biological Oxygen Demand

• Dissolved Oxygen

• Chemical Oxygen Demand

• Toxic inorganic substances

• Toxic organic substances

• Radioactive substances

Biological parameters of water quality

• Bacteria

• Algae

• Viruses

• Protozoa

• Indicator organisms such as coliforms

Read more on the parameters here

It is important to remember that water quality requirements differ depending on the proposed used of water. Thus, water unsuitable for one use may be quite satisfactory for another and water may be considered acceptable for a particular use if water of better quality is not available.

How is water quality measured in India?

The five basic water quality parameters are dissolved oxygen, temperature, electrical conductivity or salinity, pH and turbidity. The Central Pollution Control Board (CPCB) of India assesses the quality of rivers, lakes, ponds, tanks and wetlands by measuring parameters such as temperature, dissolved oxygen, pH, conductivity, biological oxygen demand, nitrates and nitrites, faecal coliform and total coliform.

• Dissolved Oxygen (DO)

The amount of dissolved oxygen is a crucial indicator of the health of a stream, river or lake and can tell a lot about its water quality. Dissolved oxygen in surface water is used by all forms of aquatic life and is also important for humans.

The concentration of dissolved oxygen in surface water is affected by number of bacteria and water temperature.

• Turbidity and TDS

Turbidity is a measure of how clean water is and its clarity and depends upon the concentration of suspended solids such as gravel, sand, silt, clay, and algae. Turbidity is an indirect measure of water clarity that determines the amount of light that can pass through the water. Total solids is a direct measurement of solid particles suspended in water determined by weight.

High levels of TDS diminish water quality. Generally, freshwater has a TDS level between 0 and 1,000 mg/L, which depends on regional geology, climate and weathering processes, and anthropogenic factors such as waste discharge.

When organic matter decays – for example from animals, plants, and algae – this becomes a suspended solid. Suspended sediments can also contain high amounts of pollutants including phosphorus, pesticides, or heavy metals.

Suspended particles diffuse sunlight and absorb heat and can lead to increased temperature of the water body, reduced light availability for algal photosynthesis and the clogging of fish gills. The settled sediment can also smother fish eggs and benthic insects.

• Nitrates

The most common forms of nitrogen used by biological organisms include ammonia, nitrates, and nitrites. While nitrogen provides the essential nutrients for all living organisms, large nitrate concentrations due to the flow of human and animal waste, industrial pollutants, and agricultural activity – can increase algae growth and reduce the amount of dissolved oxygen in the water, killing fish and other aquatic life. Nitrate can also be formed in water bodies through the oxidation of other forms of nitrogen, including nitrite, ammonia, and organic nitrogen compounds such as amino acids.

Studies in India show that a nitrate concentration in drinking water of more than 45mg/l has been found to threaten human and animal health. The CPCB (2019) has set the water quality limit for ammonia under the fishing and propogation of wildlife at 1.2mg/l or less.

Conductivity

Conductivity is a measure of the ability of water to pass an electrical current and is influenced by the presence of dissolved ions, salts, and other substances. This measure provides valuable information on the environmental conditions that aquatic organisms face. Low conductivity levels in freshwater systems may indicate normal conditions, while higher levels indicate contamination or eutrophication—the excessive nutrient enrichment of water bodies. When water conductivity is high due to elevated ion concentrations, aquatic organisms may experience osmotic stress. Water bodies with elevated conductivity may have other impaired or altered indicators as well. In rivers and lakes that have an outflow, the conductivity usually ranges from 10 to 1,000 µS/cm.

• Salinity

Salinity is a measure of the amount of salts in water and can also influence the survival of animals such as fish living in the water. Dissolved salts increase both salinity and conductivity, hence, the two are related.

• Coliform bacteria

The presence of total coliform bacteria, faecal coliform bacteria and E. coli suggests that a water body has been contaminated by faecal matter (e.g.: through untreated sewage discharge). As per CPCB (2019) guidelines, for bathing (outdoor) the Total Coliforms Organism MPN/100 ml have to be less than 500.

• pH

pH illustrates how acidic or alkaline a water body is and is expressed on a scale ranging from 0 to 14. Low numbers indicate the degree of acidity in the water; higher numbers how basic water is. A score of 7 is neutral. Major changes to pH scales can have damaging impacts on fish and aquatic life. pH values between 6.5 and 8.5 usually indicate good water quality. The CPCB (2019) guidelines on water quality for fishing and propogation of wildlife have set the pH limit between 6.5 to 8.5.

• Water temperature

Water temperature is also an important indicator of water quality and aquatic organisms such as fish depend upon specific temperatures and water conditions for their survival, growth, metabolism, health, migration, reproduction etc. temperature fluctuations affect vulnerability of aquatic organisms such as fish to parasites, pollution, and disease.  The water temperature also affects other parameters of water quality, such as dissolved oxygen. It has been estimated that a 1 °C change in water temperature can alter the metabolic rate in fish by 10 percent.

Freshwater ecosystems are dynamic and affected by water quality changes/pollution

Freshwater bodies are inhabited by plankton - which include many small sized organisms (zooplankton) or plants (phytoplankton) that typically float in the water or are carried around or wander around using water currents.

Phytoplankton form the base of the aquatic food web by functioning as primary producers that also serve as food for both the tiny zooplankton and also for larger animals such as whales.

Phytoplankton are crucial for the survival of life in the water and for maintaining the ecological balance of freshwater bodies such as rivers, lakes and ponds. They have chlorophyll and use sunlight to produce energy through the process of  photosynthesis. They consume carbon dioxide, and release oxygen. Some phytoplankton also consume other organisms to get additional energy.

The common types of phytoplankton include cyanobacteria, diatoms, organisms such as dinoflagellates, green algae, and one celled plants such as coccolithophores.

Phytoplankton survival and growth depends on the availability of  nutrients such as nitrates, phosphates, silicates and calcium in the water. Some phytoplankton can also  fix nitrogen and can grow in areas where nitrate concentrations are low. They also require trace amounts of iron. Other factors that influence phytoplankton growth include water temperature and salinity, water depth, wind and the kind of predators grazing on them.

What happens when large amounts of sewage enters water bodies

Algal blooms can occur in freshwater, marine water as well as brackish (a mixture of fresh and salt) water and can appear like foam or scum on the surface of the water and can change the appearance of water to green, blue, brown, red.

Certain species of phytoplankton produce powerful biotoxins leading to harmful algal blooms that can cause damage to animals living in water. After massive blooms, dead phytoplankton sink to the ocean or lake floor. The bacteria that decompose the phytoplankton deplete the oxygen in the water, suffocating animals such as fish that live in the water resulting in a dead zone devoid of oxygen.

Algal blooms also limit light penetration, reduce growth and cause death of plants near the shores of the water bodies (littoral zones) while also affecting the ability of organisms living in the water such as fish to access food.

Studies in India show that most of the algal blooms are triggered due to excessive amounts of phosphorous in the water sourced from agricultural runoff,  fossil-fuel burning, wastewater and detergents.

Human activities are further increasing the rate and extent of eutrophication due to discharge of nutrients such as nitrogen and phosphorus from industries and discharge of untreated sewage, wastewater, manure and fertiliser runoff from agriculture.

Other than hypoxia or low oxygen, neurotoxins and methanol produced from algal blooms can also be highly toxic to fish. Fish show fatal symptoms such as difficulties in respiration and swimming, wrinkling and fragmentation and reduction in growth and maturity, when exposed to high concentrations of methanol.

Water pollution from industries and agricultural runoff can also kill fish

Heavy metals can also lead to fish deaths as they can accumulate in the smaller animals living in the waters and impact the food chain when larget animals such as fish consume smaller animals such as phytoplankton or zooplankton. Industrial effluents from the industries located at Kanpur, Varanasi, and Kolkata include heavy metals, such as cadmium, lead, and mercury, copper, cobalt, and zinc that get deposited in the rivers such as Ganges and Yamuna have been found to lead to mortality among fish.  Organochlorine pesticides and polychlorinated biphenyls (PCBs) that get deposited in rivers in India through agricultural runoff can also kill dolphins and other kinds of fish.

What are the possible solutions to this issue?

• Decentralised governance and local management of the incident is important

Devising locally appropriate prevention and remedial actions to take care of fish kill incidents and pollution of water bodies is essential.

• Prevention is the best way out

Preventing sewage and harmful industrial and pharmaceutical effluents from entering into water bodies through implementation of stringent laws is extremely important to retain the health of freshwater bodies.

Developing policies and plans that encourage and direct funds towards better wastewater management and solid waste management mechanisms is the need of the hour.

• Developing regular monitoring mechanisms for early warning are critical

Regular and seasonal monitoring of the water quality of the waterbody through use of new technologies such as sensors to get real time data on the fluctuations in the quality of water in the water bodies is crucial to provide early warnings, ensure regulatory compliance, devise interventions to deal with pollution and assess the effectiveness of interventions.

• Community involvement is crucial to prevent these events from happening

Encouraging participatory management of freshwater bodies can also help in scaling up restoration efforts from the bottom up and prevent such events from happening in the future.

Involving local citizens groups in the process of planning, monitoring, discussing problems and solutions through cultivating a sense of shared responsibility and ownership for local water bodies to be able to arrive at collective resolutions can go a long way in restoring the health of freshwater bodies and preventing such events from happening in the future.

This has already been happening in Pune with the Pune River Revival Group, a vibrant collective of organisations and citizens in Pune who have been directing attention at the poor state of the river and the need to restore the health of the Mula Mutha by preventing sewage from entering into it. Citizens in Pune are now raising questions on the River Front Development project planned by the government that focuses on concretisation without dealing with the problem of untreated wastes from getting into the river, threatening its ecology.

• Ensuring that the flows of freshwater bodies are retained

Poorly planned infrastructural projects that do not consider rivers, streams as living flowing entities supporting rich biodiversity and negatively affect river flows can spell doom for river quality and fish that inhabit the rivers. Planning projects that do not disturb the freshwater ecosystems and help the survival of the rich biodiversity of the water body should be encouraged.