I am reading the literature regarding effluents vs. river discharge. What I find out in several sources is the river discharge is 38.9 Km3 yr -1(Bernhard Peucker-Ehrenbrink, 2009) and the global wastewater discharge is 359.4 Km3 yr−1 (Edward Jones et. Al., 2021).
The obvious question is, how can the wastewater discharge be much higher than the freshwater discharge?
To elaborate even more on the question, The river discharge is estimated to be ~20-30% of the precipitation. This leads to the conclusion that each drop of rain is being used twoc - three times before it evaporates or discharged wich also seems way too high.
Peucker‐Ehrenbrink, B. (2009). Land2Sea database of river drainage basin sizes, annual water discharges, and suspended sediment fluxes. Geochemistry, Geophysics, Geosystems, 10(6).
Jones, E. R., Van Vliet, M. T., Qadir, M., & Bierkens, M. F. (2021). Country-level and gridded estimates of wastewater production, collection, treatment and reuse. Earth System Science Data, 13(2), 237-254.
The global effluent discharge being about 10 times that of river discharge may seem counter-intuitive, but it can be explained by a few factors.
Firstly, effluent discharge includes not just domestic wastewater from households, but also industrial effluent and agricultural runoff, including fertilizers and pesticides. These sources can contribute significant amounts of effluents.
Additionally, while river discharge is measured at a single point along a river, effluent discharge is typically spread over a larger area, including both point and non-point sources, which can make it more difficult to measure accurately. This means that while river discharge may appear to be lower on paper, the actual volume of water being discharged into the environment may be greater due to effluent discharge.
Furthermore, human population growth and urbanization have led to increased effluent discharge due to increased wastewater production, and the discharge of untreated or inadequately treated effluent can further contribute to the problem.
In summary, the higher global effluent discharge compared to river discharge can be attributed to the presence of non-point sources of effluent, inadequate measurement and monitoring of effluent discharge, and increased human activities leading to more effluent discharge into the environment.
According to me, if it is really true that World effluent discharge is 10 times the river discharge, then the reasons are:
The effluent water is not only a product of river water, but also groundwater, spring water, pond water, etc. More over, the river water withdrawn for various purposes such as industries, agriculture, etc, from various points of the river stretch is not accounted in the river discharge.
N B Narasimha Prasad, your answer only makes me wonder:
what you say is that effluents are not only a product of rivers but:
A significant amount of the groundwater will become springs that will later become river discharge so things still don't add up.
Also, you say according to me, you mean that you have a peer-reviewed paper that compares the two numbers?
I don't have any literature to support or contradict the figures. I have tried to give the possible reasons for such a situation (10 times discharge), which is up to you to agree or disagree.
Groundwater, what I meant is the water extracted through borewells or tubewells from a depth below the ground. The source of water may be river or rain water. Spring water and groundwater in that way different. River discharge is largely dependent on that years rainfall, but the other sources are accumulated over a period of time or delayed response.
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