A HISTORICAL IRRIGATION SYSTEM
Leena mehendale, I.A.S. Ex-Commissioner, Nasik Division
The district of Dhule, located on the north-west tip of Maharashtra should be of special interest to any student of “Management of Irrigation Systems”, not because of the thousand’ - crore Narmada - Sagar dam alone but because the contrast provided by yet another irrigation system in the same district. Dhule district is blessed with two mountain ranges - Satpuda lying east - west and Sahyadri lying north - south and with three major rivers - Narmada arising in Vindhya, Tapti arising in Satpuda and Panjhara arising in Sahyadri. It has six tribal talukas where literacy rate in only 10%, both tribal and non-tribal areas are comparatively backward. Major occupation is agriculture and main deciding factor for a good or bad year is the rainfall.
The river Panjhara flows west to east in southern parts of the district, covering two talukas Sakri and Dhule. Then it skirts the city of Dhule, takes a U-turn, goes northward, then westward to meet Tapi and continues westward till they meet the Arabian sea after travelling in Gujarat
An Irrigation System of major importance built on Panjhara and its two tributaries nearly three hundred years back has been a predominant factor in deciding the cropping pattern and economy of these two talukas. The system consists of a series of earthen or stone dams, nearly 70 in number, built along the length of the river Panjhara supplying drinking and irrigation water to nearly 35 villages and irrigating nearly fifteen hundred Hector of land. They are working without the problem of silting, or maintenance.
My interest in this system was aroused when I was told that Dr.Vishweshwaraiyya, one of my childhood idols, had built them. That was not so-they were built three centuries back during Peshwa regime. But Dr. Vishweshwariyya has worked here as an irrigation engineer and one can feel proud that he must have seen these dams, imbibed their greatness, studies them, before he proceeded to achieve new heights for the country.
The system is very different in its concept and management from the present - day system . While modern systems provide a static storage, these dams work on a dynamic concept of storage which appeals greatly to one’s intelligence.
How do these dams function? To start with, a stone dam (sometimes earthern) is built across the river bed to obstruct the water flow and create a small storgage. But water availability for irrigation is not decided by this dam - height or this storage. In fact these dams are not higher than 8 to 10 feet from ground level. Water is diverted from here by building a retaining wall along the length of river, height of the retaining wall goes on reducing till it reaches ground level. At any suitable place along the retaining wall, a canal is started which will carry water to the far off fields in that village by gravity. The capacity of canal is small so that water in excess of its carrying capacity goes along the wall and finally falls back into the river.
Thus, it is the height of retaining wall at the mouth of the canal and the canal width which alongwith the dam storage, will decide the water availability in canal at any given time. I call this a dynamic storage because water is not static here, but is always flowing into the dam, from there to canal and from there to the fields. Thus when there are no rains, or no flow in the river, no irrigation water is available. But even when there is a flow, the maximum quantity of water available at a given time is predetermined by technology itself and nobody can claim or get more than a particular quota of water on a given day.
Interestingly, there is one way of getting irrigation water for a longer period . The total rain water received in the mountains finally runs down into the sea or the underground acquafers. If this run-off velocity can be reduced such as by having denser forests and trees on the mountains then the total water received by the mountains will flow for longer duration in the river.
In the modern dams also , we build a wall across the river and stop the water flow and store the water. But unlike the Dhulia system, the stored water is blocked completely and not partially. This storage can be used throughtout the year and some minimum water can be assured even when there are no rains. But this is only in theory. Because the other presumption also exists only in theory - namely that a ceiling will be put on use of maximum water by one individual.
This presumption is in fact the most important condition for the successful and equitable distribution of the available water. But the effective implementation of the condition is left in the hands of administrative machinery. Unfortunately this administrative set up is neither free from corruption nor immune to the pressure from the mightier - as we have painfully learned in these forty years of independence. The result is obvious. Though the manuals of irrigation department lay down strict ceilings on the maximum quantum of water to be supplied to each beneficiary, it is a common practice to procure more water - sometimes even upto twenty times the allotted quota by adopting dubious methods which need no listing.
Thus the principle of ceiling, presently administered by human machinery has failed in the modern dams. In Dhulia type, the ceiling is put by the technology itself . No matter how great the rainfall, any given field or “fad”, as it is popularly known will get only a fixed quantity of water during the rainy days. The disadvantage is that during non-rainy days water is not assured - but then over a large number of years, farmers have formed their own judgement of water availability during off - season and have fixed their cropping pattern. In fact since the Panjhara originates from Sahyadri, tiny streams of water continue to supplement it for a longer period. So the availability of water is for a longer period than the rainy season. It cannot of course be called a perennial availability.
The farmers have also finalized a cropping pattern that works beautifully without problems of salinity or quarrels over water distribution. Entire irrigable land of one village is divided in three ‘fads’ - fad meaning a continuous patch of land comprising the lands of may farmers. Only three crops are allowed - one in each fad - namely sugar-cane, wheat and jawar, and every fad must rotate its crop every year thus having a three year cycle. So we also automatically know the area under wheat & sugarcane and jawar every year.
The disadvantageous consequences of modern dams is that while areas near the dam profit by it, the tail ends are always faced with uncertainty of water supply. Secondly the down stream areas are deprived of their drinking water supply. The canals have to carry a huge water supply initially and we have had various problems of canal damages. Government had to incur heavy expenditure on their repairs and maintenance year after year. In fact in some major dams, the canals were damaged even before water supply had started - thus increasing the gestation period by six to eight years.
In comparison the old canals on Panjhara are much smaller in extent - they carry smaller volumes of water - their repairs and maintenance is less frequent and easier, and is managed by the beneficiary group through contributive labour. The small worked beautifully after all.
It is to be noted that the water supply in down-stream villages, right upto Dhulia city will be severely affected if any village decided to increase the height of their dam. To avoid this, every year a committee of villagers from all the villages inspects the dam height, the canal condition and decrees upon the beneficiaries of any Village to undertake repairs to canals and maintain the dam height through Shramadan or collective labour. The Peshwas are said to have introduced a system of fine if any Village tried to increase dam height or tampered with the steady river water flow in any other manner. But is has never become necessary to actually levy and collect the fine.
Another comparison which my mind drew was on the problem of silting of dams. For a modern dam, the silting will be useful only till it fills up the dead - storage volume but thereafter it is a sure menace because it starts reducing the holding capacity of th dam - thereby adversely affecting the guarantee of minimum water supply.
In case of dynamic dams however, the more the silting the better - because then the overflow in the further parts of the river increases while the concerned areas still continue to get water what they were getting before.
All this is not to suggest a judgement on the desirability of modern dams. The only point I want to make is that this age old technique of bandharas has been abandoned now in favour of the modern technique of building dams. The technological progress must be commended. However, we need not totally abandon the older technique and must recognise it as an available alternative.
Two points of minor significance also need to be mentioned. Each of these bandharas - whether modern or older is prone to water stealing by neighbouring farmers who can take a well in the nearby field. The well will keep on getting charged and water can be lifted from it. The answer to this problem will be same in both cases. Another observation is that along the entire length of river with this chain of old bandharas. I noticed a good green cover and every bandhara was a mini bird sanctuary where birds of different species were flocking in large number. If a large dam upstream results in drying up of these small bandharas - the birds will have a tough time - because they normally take a long time to learn that they should also shift upstream.
No comments:
Post a Comment