Setting the Scene
Over-abstraction for irrigated agriculture is the main reason why the Ramganga river—a headwater tributary of the Ganga—is almost dry in some parts of the year. It severely compromises the health of the riparian eco-systems and is a principal contributor to the poor quality of the Ramganga waters. Of course, the other key contributor to the river’s poor health is the high pollution load.
What can be done to increase dry season flows and meet environmental flow requirements?
A solution would be to increase large-scale reservoir storage capacity. On one level this would make sense since the Ramganga basin is subject to a unimodal rainfall regime and some 80% of flow in the river is recorded in the monsoon period. Note that the Ramganga—in contrast to many other Ganga tributaries—is not glacier fed. However, establishing large-scale water storage infrastructure takes time and is expensive, but is also controversial. There are many good reasons why people object to building a large dam. Perhaps better, therefore, not to rush this option and first carefully consider the consequences.
Thus, a more practical approach in the short and medium-term would be to lower water abstractions. Either by reducing the command area—which seems unrealistic from a political perspective because of the large rural population—or by increasing water productivity in irrigated agriculture. This text is about the latter.
Unreliable Water Delivery
The below figure presents a causal diagram of the water delivery system in a typical public irrigation scheme in the Gangetic plain in the Ramganga basin.
At the core of this conceptual model sits ‘unreliable water delivery’. This is somewhat surprising because irrigation should, in theory, provide full water control. Nevertheless, unreliable timing of water delivery appears to affect a considerable part of the command area and is not limited to the tail-end sections only (Ramganga Basin Plan, March 2020). It is caused by a combination of factors which include:
- High sediment load in the river (during the monsoon period) that leads to sedimentation of canals and water control structures, and necessitates regular and expensive maintenance
- Gravity irrigation with surface water from a highly seasonal river through a dendritic canal system that has few redundancies, and without alternative water supply options
- Inadequate water storage capacity within the irrigation scheme
There are several consequences of the absence of water security within considerable parts of the irrigation scheme. For one it leads to over-irrigation. Many farmers (in water-insecure sections) try to get as much water as possible when it is available, even if it is not their turn in the roster. After all, they are not sure when the next water delivery will be. Over-irrigation, obviously, compromises water security in the areas further downstream, but can also cause water logging and salinization. Water logging is further aggravated by sporadic high rainfall events in combination with poorly functioning drainage canals because of siltation.
The Ramganga Basin Plan reports that some 20% of the command area is now affected by water logging. It represents a waste of scarce water resources that could otherwise have remained in the river to support dry-season flow.
Absence of water security also causes conservative farming practices. Thus, high yielding (commercial) agriculture is generally concentrated in the upstream parts of the scheme—where water supply is more reliable—while less-productive smallholders are over-represented in the more downstream parts of the command area.
What can be done to enhance in-scheme water security?
High Sediment Load
The high sediment content of irrigation water abstracted from rivers is the root cause of unreliable water delivery. It is to a large extent caused by natural processes: geology, steep slopes in the upstream catchments, intense rainfall, landslides, frequent seismic activity, etc. It is unlikely that interventions—such as soil & water conservation efforts, measures to reduce sediment dumping during road construction, or afforestation—will fundamentally change the influx of sediment in the Ramganga and its tributaries. Therefore, the high sediment load in surface irrigation water is probably a fact of life.
So, what other options do we have?
Groundwater Potential
An interesting feature of the Gangetic plains is the existence of considerable groundwater resources. The plains immediately adjacent to the Himalayan foothills have deep alluvial soils with high groundwater recharge capacity. In addition, rainfall in this area is quite substantial and exceeds 800 mm per year. Hence, the difference between pre- and post-monsoon groundwater levels in this zone is generally between 0.5 and 1 m (Ramganga Basin Plan, March 2020). It represents a large annual storage of water.
However, groundwater irrigation is currently discouraged in the irrigation schemes in the Ramganga basin, probably for fear of over-abstraction. For instance, there are restrictions on state-operated tube wells in the canal command area. In addition, groundwater irrigation is expensive because of pumping costs. Canal water, by contrast, is cheap because irrigation fees are charged on a crop basis and not on actual water consumption (Ramganga Basin Plan, March 2020).
Nevertheless, increasing the use of groundwater—in a semi-decentralized setup; pumped and managed by the irrigation authorities rather than by individual farmers; on an ‘as and when needed’ basis—in the downstream sections of the command area would address multiple problems. It would 1) reduce the dependency on (unreliable) canal water and thus provide water security, 2) address water logging, 3) offer the possibility to make better use of substantial but unreliable rainfall, 4) increase water productivity, and 5) reduce water abstractions from the Ramganga and tributaries in the dry season. Moreover, it will probably also lower canal maintenance costs.
It goes without saying that groundwater abstractions must be carefully monitored and managed to avoid lowering of the water table and depletion of aquifers. But, given the size of the groundwater resources, that is a technical problem and a matter of finding the right (multi-year) balance. It will probably differ for every scheme, and even for every section within the scheme.
In-scheme water storage
Another option to improve in-scheme water security is to establish more (small-scale) water storage capacity within the command area. Decentralized (small-scale) water storage increases the resilience of the water delivery system, offers the possibility to make better use of rainfall, and serves many other purposes. Moreover, it is probably cheap. However, the Ramganga Basin Plan reports a widespread and accelerated reduction of small pond areas. It is not clear what is behind this reduction of small ponds. It is certainly something to investigate.
Closing Comments
Increasing dry-season flows is a key element of any strategy to improve the health of the Ramganga river. This post argues that it can be achieved without reducing the area under irrigation, or without major institutional reforms within the schemes (which are always difficult). In fact, it can be achieved while simultaneously improving the performance of irrigated agriculture. The solution centers around strengthening in-scheme water security by making strategic use of groundwater resources in selected sections of the command area, in combination with increasing small-scale and decentralized water storage capacity. It would reduce—or even negate—the need for over-irrigation and make better use of rainfall, whenever that is available. Obviously, improving water productivity—by reducing wasteful use—implies that more water can stay in the Ramganga and its tributaries.
Besides, secure water supply is a prerequisite for agricultural modernization.
The above analysis is conceptual. Specific solutions will differ per scheme or even within schemes. It goes without saying that over-abstraction of groundwater needs to be avoided. Nevertheless, the discussion hopefully offers a useful perspective that can support the ongoing efforts to improve the health of the Ramganga river.
Postscript
In the lower areas of the command area—as well as in areas far removed from the canal system where water supply is uncertain—groundwater irrigation with private tube-wells is widespread. Officially it requires a permit but in practice this rule is not enforced. Since the water table is generally shallow, excess use of irrigation water is common. It leads to waterlogging, salinization in some areas, and gradually declining groundwater levels. But it also provides water security and yields are very reasonable (about 4 tons per ha for rice and wheat in the Gangetic plain in Uttarakhand). It appears that individual farmers have already adopted the strategies proposed in this post. Nevertheless, measures are required to avoid over-irrigation and receding groundwater tables. It calls for some level of regulation of the tube-wells to avoid over-extraction, in combination with sensitization efforts to increase water productivity and training of farmers in determining field irrigation water demand.
REFERENCE
Ramganga Basin Plan – Volume 1; State Water Resources Agency; Government of Uttar Pradesh; March 2020