Question

Complete the tables below by indicating whether the physical, chemical and biological parameters change with the course of a river.

Please include a valid reason (NO PLAGIARISM!)

. Chemical
. Parameter	Increase/ Decrease/ Unchanged In Downstream Direction?	Reason(s)
. pH
. Temperature
. Dissolved Oxygen
. Metals
. TSS
. Total Nitrogen
. Ammonia
. Total phosphorus
. Chloride
. Sulfate
. Salinity

Answer 1

1. pH

pH should reduce downstream (acidity should increase). This increase of acidity can be attributed to the release of acid-forming substances such as phosphates (from detergents), sulfates and nitrates into the water body. Also, the geology of underlying rock contributes to the increased acidity. pH depends on the nature of deposits over which they flow.

2. Temperature

Temperature increases downstream. Higher temperatures can be attributed to the anthropogenic influences like clearing of riparian vegetation for timber and settlements. Overgrazing by livestock reduces the shaded area, warming the stream thus increasing the temperature. Discharge of industrial effluents also increases the water temperature. Some community and land-use practices are also responsible for higher temperatures.

3. Dissolved oxygen

Dissolved oxygen decreases downstream as algae and submerged plants die and decompose consuming dissolved oxygen. The oxygen solubility also decreases as temperature increases which happens downstream.

4. Metals

Some heavy metals (like Mn, Ni, Cr, Cd, Cu, Pb, Hg, etc) have a tendency to accumulate downstream. Their concentration increases downstream because of excessive industrialization use of fertilizers. Their concentration is also dependent on the pH and concentration of other heavy metals like Aluminium.

5. TSS

Total Suspended Solids increases downstream because of increased erosion in waterbed and resuspension of particles deposited in riverbed. Deforestation and intensive farming also increased erosion.

6. Total Nitrogen

Nitrogen occurs in the form of ammonia, nitrate, nitrite and ammonium ion. The total concentration of nitrogen increases downstream, which can be attributed to the increase in surface runoffs from agricultural lands, animal pens and communities into the river.

7. Ammonia

The concentration of ammonia increases downstream owing to the use of manures and fertilizers in agricultural lands with risk increasing further with heavy rainfall.

8. Total phosphorous

It increases downstream because of the excessive use of fertilizers by farmers and the increased use of detergents by women for washing.

9. Chloride

It increases because of road salt runoff, sewage, water conditioning salts, and fertilizers. The effect of evaporation is also there.

10. Sulfate

It increases because of the excessive use of fertilizers by farmers. Also, under anaerobic conditions, Thiobascillus converts pyrite to sulfate.

11. Salinity

It increases downstream as river water is used for irrigation in agriculture while drainage water from agricultural land is returned to the river downstream. High salt concentration in drainage water is due to evaporation.