DESILTING MALAMPUZHA RESERVOIR, PALAKKAD DIST., KERALA, INDIA:

DESILTING MALAMPUZHA RESERVOIR, PALAKKAD DIST., KERALA, INDIA:

ECOGEOLOGICAL OBJECTIONS

Dr.Thrivikramji.K.P. thrivikramji@gmail.com

(An English language version of a talk presented in a seminar organized by Malampuzha Dam Samrakshana Samithi, in Palakkad, July 11, 09)

It is 55 yr., since commissioning of the Malampuzha dam and the Malampuzha lake in Palakkad dist. of Kerala. The KERI (Kerala Engineering Research Institute) came up with a suggestion that the reservoir already lost 12% of the reservoir capacity due to the siltation. Walayar, another tributary of Kalpathipuzha, has a smaller dam and reservoir (Walayar reservoir) upstream of confluence of Malampuza and Kalpathipuzha. Both dams have been built on the right bank tributaries rising from the western ghats on the northern escarpment of Palakkad Gap.

Table: 1. Vital facts, Malampuzha Reservoir, Palkkad..

River basin	Bharathapuzha
Dammed Tributary	Malampuzha
Catchment area	147.63 km2
Reservoir Capacity	226 mm3
Water spread at FRL	23.13 km2
Level of siltation (KERI) Level of “garbage” (NRSA)	12% or 27.12 mm3 17.0 mm3 or 7.5%
So sediment volume	Between 17 and 27 mm3

In the Budget speech for FY09, the minister concerned made an announcement in the state assembly, following a recommendation of the water resources ministry, a program of desilting of the Malampuzha lake will be implemented at cost of Rs.800 crores and at net revenue of Rs.400 crores out of the sale of sand and mud in the sediment in the lake. Undoubtedly and seemingly, a definitely worthwhile and pragmatic proposal.

Yet, the issues of desilting are not about making additional revenue or raising the storage of the reservoir as the desilting is loaded with umpteen eco-geological problems about which no transparent answers are offered by the concerned authorities of the government.

First and foremost of all, my questions are:

1. Is there such a reserve of silt or sediment in the reservoir?. As an advance answer, I will say there is no such quantum of accumulated silt in the lake basin.
2. What management practices and technological solutions have been readied to overcome the sediment plume rising in the reservoir water and contaminating the sole drinking water source of 20 million humans in and around the Palakkad town?
3. Will the sediment laden water be fit for irrigating the cultivavable fileds in the ayacut as the soil characteristics may slide to a different consistence and nature perhaps even deleterious to the crops at least in the short or medium terms?
4. What is the fate of the mud (silt and clay) once the sand fraction (15%) is removed for sale? (A proposal is to sell the mud to the Burned brick industry?)
5. Will the highly organic carbon laden mud be acceptable to the brick industry? If they reject how and where the mud will be disposed?
6. In addition to sediment, the catchment also supplies dissolved chemical ions in to the reservoir waters, from the farm residues of fertilizers as well as biocides. The loading of such in the sediment will be at least a 100 times larger than its level in the water. Have the quanta and species of these ions have been ascertained before hand and made public to allay the fears of the civil society of Palakkad?
7. When the sediment comes out of the reservoir into the washing plant, it is logical that two fractions of sediment, viz., sand and mud will be stored separately in the storage areas and will be subject the wind (currents) which will hasten the drying the top layer of stored materials. The finer mud grains will be picked up the wind and resulting in “duststorm” like contexts, harming the lungs of the very young and older citizens and the other immuno-compromised members of the society. In fact we have been enjoying the Palakkadan Kattu season from time immemorial. To further worsen the situation; in the aerosolic mineral particles (chiefly clay), several lethal and non-lethal chemical radicals will enjoy a piggy ride.
8. Now it is the question of the sediment volume. Take for example some specific aspects of the Malampuzha lake. No detailed topographic survey at a scale 1:1000 or 1:2000 exists, other than the SOI toposheets of 1:63360 scale. It is precisely so in respect of all the reservoirs of the state of Kerala and of India in general. This study/mapping is considered as “unnecessary” expenditure while proposing the estimate of the investment.
9. What is available now is the bathy chart of sediment water interface of the Lake. As Pre-lake map of the basin of a very gross scale, despite the accuracy of the map of the sediment prism and its size in the reservoir shall be far from precise. As far as I know, no “sparker” survey has been under taken yet to establish the bottom or base of the sediment prism enabling a better precision in the quantum of sediment.
10. But NRSA went one step ahead using DGPS (?) and other satellite image based technologies and came up with a an estimate of “garbage” in the lake bed at 17.0 mm3, roughly half of what KERI came up with. I shall assume that the truth is somewhere else and would take the NRSA number as a ceiling figure. So the lost storage of the reservoir is at variance with the proposal of KERI and used by the water resources ministry to launch a scheme of desilting of the reservoir. And this accumulation took a span of 55 yr.
11. For argument sake, at the rate of 27.0 mm3 rounded to 30.0 mm3 per every 55 yr., it might take 400 yr. for the lake to become a marsh. Or the lake will loose 50% storage only by 150 yr. from today. From the eco-geological point of view I do not see any compulsion for desilting Malampuzha Lake to day or ten years from now. The only counter point is that the sand in the sediment is a commodity in short supply in the state and this program will go a long way in saving the rivers of Kerala.

Now let us take a closer look at problems of handling the mud after removal of sand. We have been given to understand that the desilting is a two year long process. Fine. But what about the strategies for preventing mixing of mud in the lake water which is used for piped water supply in the region. And removal also will undoubtedly result in the destruction of the ecosystem and the food pyramid of the lake. The depth to the photic zone (depth of reach of sunlight) will contract to adversely affect the life in the lake.

Further, even if a modern suction dredging technology is used, the region or a pond that collects the slurry of mud after removal sand fraction will be quite large attracting scavenging birds and animals- a local irritant and nuisance however short lived it is.

Obviously one pond is insufficient, as the plans are to separate water from the slurry to collect the mud for sale to the red-brick industry. In fact a battery of ponds will be needed to handle and clarify the large volumes of the mud slurry to ready the mud for sale. A problem which is part of the operation is wind blowing over the mud spreading the mud particles and smell in the downstream regions of wind to the dislike of the public and even can harm the very young and very old.

Then, what are the plans for handling the water used in the sand washing plant? Where ever this water is headed, say the river or the canals or the farmlands, everywhere it will lead to one or other harmful consequences, either to the water, or to the soil or both to air, water and soil. Are there any new technologies easily available to counter such harms? Let us not ignore the fact that, the entire process is to take place in the backyard of a population center. When many of the villagers in Plakkad depend on tanker lorries for drinking water during part of the year, the government is toying with the idea of sand washing and separation. What a paradox?

My own rough estimate tells me that if the mud is stacked in a tower of vertical walls, in a patch of land of 1.0 km2 area it shall reach a height of an eight storey building.. In other words, if you like, the stack would rise to the height one storey in an area of 8.0 km2. As a gross estimate of sand in the sediment is only 15%, imagine the huge bulk of mud after washing and removal of sand fraction. Moreover, the water seeping from stacks of mud would have high loads of dissolved chemicals whose environmental safety is still an open question. We are unsure of the surprises this water might pose. Wise decision will be to prevent this water from escaping into the surface or subsurface water sources of the region.

Therefore my earnest view is that before implementation of the desilting program, a research study needs to be undertaken addressing the short-, medium- and long-term impacts to the civil society, soil, water and air of the region around Palakkd. I propose a careful scientific scrutiny of impact on the a) lake and life in the lake, b) sand separation and mud handling and storage before shipment, c) the region and people around a 10.0 km radius of the center of operations and a cost benefit analysis on the basis of proven reserve of sediment in the lake and all these with a fair degree of transparency.

Finally, my gut feeling is, as this lake takes at least another 150 yr to loose 50% of the storage, that we leave the Malampuzha lake undisturbed, with which the Yakshi of Malampuzha garden will concur with.

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