East West Grand Canal Of Nepal, Part II

We propose to utilize the freely available canal-top air space for installation of solar panels to produce electricity and to reduce evaporative water loss in the canal while allowing for water navigation on the canal

July 29, 2020, 10:55 a.m.

Introduction

In a paper some weeks ago, we introduced the concept of a multi-purpose East-West Grand Canal in Nepal. We had briefly touched upon the cascading impact of the Covad-19 pandemic on the already sluggish Nepali economy. Nepal’s economy relies significantly on the remittance by its workers abroad. The current crisis could be utilized as an opportunity to create a vision for large programs to mitigate the impending economic and social disaster to spur economic growth. Nepal must invest in ambitious and smart infrastructure projects to propel the country towards increased prosperity levels. With this backdrop, we had proposed an East-West Grand Canal, which could be one of the game-changing projects for Nepal.

The proposed Grand Canal can irrigate some 8,000 square kilometers of land that is not currently irrigated in the Nepali plains, generate a significant amount of solar power, produce some hydropower as a byproduct, usher an era of commercial water navigation, recharge the ever depleting groundwater, help control flood, and promote opportunities for tourism and recreation generating thousands of direct and indirect jobs. In this article, we expand the initial concepts and provide a high-level overview of some technical, environmental and social issues related to the different aspects of the proposed canal project.

Canal-top Solar Energy Generation

We propose to utilize the freely available canal-top air space for the installation of solar panels to produce electricity and to reduce evaporative water loss in the canal while allowing for water navigation on the canal. To accommodate all these objectives, the provision of a required clearance between the top of the water surface in the canal and the bottom of the structure supporting the solar panels is important. Looking at the examples from similar waterways, that clearance should be preferably10-15 meters. This should also be the minimum clearance for the portion of the main canal under any bridge.

To save installation costs and optimize electricity generation, it is proposed that canal-top solar panels be facing south at a fixed angle of about 25 degrees from the horizontal plane. A simple structure made from steel truss and girders can support the weight of the panels. As the general alignment of the main canal is east-west, installing south-facing solar panels along the length of the main canal will become feasible and easy. Solar panels could also be deployed over the branch canals. If the construction of a structure required for a vessel (Class IV and V) passage turns out to be too high, it may be more prudent to have solar panels only on the non-navigable branch canal tops, where they could be installed at a lower height of around 3-4 meters. The lands procured on both sides of the main canal as the canal right-of-way are yet another alternative location to deploy solar panels. However, in this case, the benefit of reducing the evaporation loss of water on the canal will not be realized.

Assuming an output similar to that of Gujarat, India, canal-top solar panels on the Grand Canal and its branches in Nepal are expected to generate about 6,000 MW electricity after the completion of entire approximately 4,000 km of the canal system, and if solar panels are installed on about 50 percent of the total canal length (Fig. 1). For comparison, in 2019, the total installed electrical power capacity in Nepal was around 1,200 MW. Another approximately 1,000 MW electricity capacity is presently under construction as of 2020. Thus, the solar power generated from the canal top of the proposed canal system would provide a significant boost to Nepal’s electricity generation capacity realizing Nepal’s long-held aspiration of being an energy center.

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Fig.1. Canal Top Solar Panels, Vadodara, Gujarat, India. Pic by A. Adhikari

The solar power generated thus could be connected to the national transmission grid. In many locations, the solar-panel generated power could be connected to the local grids to provide power to the nearby communities. The benefits of solar power include using the power in a modular fashion, i.e. utilizing only the distributed generation to local areas without connecting the power to the national grid. As solar power is available only during the days with sunshine, battery storage of the electric power, and supplementing it with wind-generated and hydro-power should be considered to provide continuous supply around the clock.

Navigation

Water navigation being a totally new area in Nepal, there are no national standards, expertise, or guidelines for the design of navigation canals. The international institutes governing the design of navigation channels are: Permanent International Association of Navigation Congresses "PIANC”, the International Association of Ports and Harbours "IAPH", and US Army Engineers. Based on their recommendations, a first-class two-way navigation canal width is determined for a design ship 7.5m wide and 50.0m long, following an Egyptian experience (El-Sersawy H., Ahmed A.F, 2005) as 58.0m at the full supply level of the canal. For a trapezoidal canal with 2H: 1V (Horizontal: Vertical) side slope and 2.0m full supply depth, the bottom width of the canal will be 50.0m. Considering a 2.0m free-board for storing incoming floods in the crossing streams, the total depth of the canal is considered 4m giving the top width of the main canal as 66m (Fig. 2).

The Grand Canal has to run along the contours at a very mild slope of 15 cms per km resulting in a discharge carrying capacity of about 80 m3/s for an unlined section with a velocity of 0.75 m/s, whereas corresponding discharge and velocity for a lined section will be about 190 m3/s and 1.2m/s. The desirable velocity for navigation canals should be within 0.50 m/s to 0.70 m/s. Therefore, the full supply design discharge of the canal is considered 100 m3/s. Its geometry, slope and lining will have to be designed accordingly and may change from section to section as the discharge changes because of the irrigation demand at different secondary canal intakes.

The ultimate goal of this inland navigation system should be to connect to the seaport at Kolkata using the Koshi river and possibly to Mongla port in Bangladesh. This will also necessitate constructing at least one large inland port near Chatara in Koshi and passenger and freight terminals at a number of appropriate locations to be decided after a feasibility study.

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Fig. 2. Schematic diagram: Traffic elements of a two-way navigation channel

Total Canal Length

One of the most challenging aspects of the canal design is to maintain the desired water velocity and the desired longitudinal geometry of the canal to realize the navigation goals. The canal must be straight as far as possible and when the curves are unavoidable the radius should be kept as large as possible. The design standard for a first-class navigable channel requires a radius of 6 times the length of the longest vessel. Therefore, meeting the dual requirement of maintaining a gentle slope by running along the contours and meeting the design requirement of the curvature is by far the biggest design challenge. The total length of the Grand Canal can be known only after a feasibility level survey and design. However, the first guess of around 1,500 km can be taken as a tentative main canal length. The secondary canals can be assumed taking off down south and sometimes to north roughly at an interval of 25 km for an average length of about 40 km (total length of two sides) making a total of about 2,400 km of secondary canal lengths. There will be a network of tertiary canals and crisscrossing field channels that will significantly change the irrigation landscape of Tarai.

Cross Drains

The east-west Grand Canal will have to cross numerous perennial and ephemeral rivers generally flowing north-south and coming from different origins (Fig. 3). Most problematic of these are the southern rivers originating from Chure, categorized in the third group above, have flowed only during the 4-months long monsoon season associated with a huge load of sediment coming down from the fragile Chure range but are dry during rest of the 8 months of the year.

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Fig.3: A schematic alignment for the East-West Grand Canal of Nepal

Irrigation canals have a simple solution for crossing such streams by using an inverted syphon (Fig. 4). However, the proposed Grand Canal being a navigation canal cannot use this option and the remaining options are a) level crossing, b) aqueduct and c) super-passage. Even super-passage can be ruled out because required vertical clearance over the canal can hardly make a super-passage feasible. That leaves level crossings and aqueducts as the only viable cross drainage solutions. The design challenge compels the engineers to integrate the proposed Canal with the existing Chure conservation project to minimize the sediment load on these ephemeral rivers. It would provide an opportunity for engineering innovation in overcoming the challenge of designing an appropriate level crossing structure. One option could be trapping the incoming sediment in a series of low check dams upstream of the crossing and an appropriate sediment flushing arrangement at the crossing location. The sediment trapped upstream at the check dams can be used as construction material generating revenue to offset the maintenance cost of the project. Whether we choose aqueducts or level crossings will solely be dictated by the required canal level at the crossing location.

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Fig. 4. Image showing an example of an aqueduct being used for water navigation

Water Availability

The most important design-related information is to have reliable data on how much water is available in different rivers for diverting into the canals. In this respect, the monthly mean flows of the Karnali river are the vital data as we have some restrictions on Mahakali, Narayani and Koshi imposed by existing treaties with India, whereas we do not have any treaty on the use of Karnali flows. Based on the Department of Hydrology and Meteorology (DHM) records, the minimum mean monthly flow of Karnali is 331 m3/s and the maximum flow is 4,139 m3/s in August (Fig. 5). Even after the low flows of Bheri are all diverted to Babai, Karnali can have slightly more than 200 m3/s in February out of which about 200 m3/s can be diverted in the canal. This confirms that a navigation canal with a design discharge of 100 m3/s to be available round the year is feasible.

Fig. 5

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Source: Adapted from the Nepal Department of Hydrology and Meteorology (DHM) data

Integration with the existing system

As suggested in our earlier paper, the existing individual canal systems should be integrated with the proposed Grand Canal. The integration should take place at the conceptual, policy, administrative and operational levels. It could be argued that part of the Grand Canal system we have proposed is already completed or in existence. A case in point is when the proposed Grand Canal meets Chatara (Sunsari district) the entire Chatra Canal system (Fig. 3) will continue to function as a branch and sub-branch canals which together irrigate about 68,000 hectares of land in Morang and Sunsari districts. Furthermore, a portion of the Chatara main canal could be turned into a section of the Grand Canal itself after necessary adjustments. To borrow an assembly line analogy from the manufacturing process, the proposed East-West Grand Canal project will be completed once all its components are completed at different times and places and they are connected as one system.

The existing canal system and irrigation project to be integrated were results of various policy initiatives and agreements such as (old) Mahakali Agreement (1920), Koshi Agreement (1954), Gandak Agreement (1959), Tanakpur Agreement (1991), and Mahakali Agreement (1996). Some of these have been revised, and suggestions to revise others have been floated. Perhaps a comprehensive agreement including revisions of earlier agreements could be reached in the pretext of the proposed Grand Canal in accordance with prevailing bilateral and international riparian water rights practices.

In addition to the above, Nepal already has several irrigation projects at various stages of completion. These include irrigation projects on Baghmati, Babai, Praganna and Badhapath, Sikta, Rani Jamara Kulariya, Palungtar Kundutar, Bheri-Babai Diversion, Sunkoshi-Marin Diversion, Dang Valley Integrated Irrigation and Power Project and Prime Minister’s Irrigation Modernization Project, which will serve as branch canals to the East-West Grand Canal.

For effective and efficient integration, the spatial and temporal distribution pattern of the hydrological characteristics of the rivers of Nepal also needs to be taken into consideration. For example, river originating in Himalayas (Mahakali, Karnali, Narayani, Koshi), in Mahabharat(Babai, Rapti, Tinau, Kamala, Kankai Mai, etc.) and in Siwalik range are fed by waters from completely different watersheds and ecosystems.

The overarching goal of this East-West Grand Canal is to fully utilize the unused precious low flows of the snow-fed large rivers mainly Karnali, Narayani and Koshi by diverting it to water deficit areas where it can be most optimally utilized. The design challenge is how to optimize this goal by integrating all planned, existing and envisioned plans, policies and projects.

To address these challenges effectively and to execute the plan in phases, a segmented look at the canal is proposed to identify challenges faced by each of them. The segments are: 1. Mahakali-Karnali,2.Karnali-West Rapti, 3. West Rapti – Narayani, 4.Narayani – Bagmati, 5. Bagmati- Kamala, 6. Kamala – Koshi and 7. Koshi – Mechi.Each of these segments has some common problems and challenges, which are mainly related to alignment, land acquisitions and cross drains and some unique challenges related to integrating existing irrigation systems, such as Mahakali Irrigation and Rani Jamara Irrigation Project in segment1, Babai and Sikta IP in segment 2, Chitwan Irrigation Project, Sunkoshi – Marin diversion and Bagmati Irrigation Project in segment3,4 and 5 and Sunsari Morang Irrigation Project in segments6 and 7. More importantly, segment 1, which is impacted by the Mahakali Treaty article 2 can be considered to have the following 3 options: (i) Run the canal from Karnali to Mahakali using Rani-Jamara alignment with necessary design revision, (ii) Run the canal from Karnali to Mahakali with a new intake just downstream of Rani-Jamara and (iii) Use India made headwork’s at Tanakpur barrage and the allotted water to design the segment from Mahakali to Karnali.

Environmental and Socio-economic Issues

A project of this magnitude and scope will have several major environmental impacts including hydrological elements such as the flow of the rivers that are connected to the canal, groundwater levels, and surface run-off patterns.

As the canal will divert large amounts of water from the rivers, there will be impacts on aquatic life in the river. The construction of the canal will also have an impact on wildlife in the area surrounding the canal. After the completion of construction too, the canal may obstruct the usual travel paths of the wildlife in the area.

By using detention and retention ponds to store excess water during the rainy seasons, the canal project will help recharge the groundwater and help raise the groundwater table that is currently being depleted due to excessive extraction. Moreover, infiltration from the canals recharges the aquifer directly and compensates for over-exploitation of surface and groundwater resources. Rapid urbanization, overuse of surface and groundwater resource, change in land use pattern, deforestation, and increase in the impervious surface has lowered the groundwater table significantly in Tarai. This will directly threaten groundwater ecosystems in the Tarai region, which the Grand Canal system can partially help correct.

The construction of the canal may also have an adverse impact on archaeological and historical resources above and under the ground. The construction of such a large-scale project would also have impacts on the human population as many people in the alignment area may have to be resettled. Also, some communities will be divided by the canal, and opportunities for social and physical connections should be provided in the project.

Mitigative measures and long-term solutions to minimize the adverse environmental and socio-economic impacts of the canal need to be planned and implemented. Lessons learned in Nepal, India and elsewhere can be utilized while planning and implementing the mitigative measures.

The canal project will generate thousands of jobs during the study, design, construction and operation of the canal system. The canals will create many scenic areas, improve the microclimate of the surrounding areas, and help in the promotion of tourism. The canal system will boost the hospitality industry and commercial development in the surrounding areas. For example, in Arizona, USA, many canal-side locations fetch high prices for their residential and commercial and commercial development potential. These locations are considered attractive as they provide for good views, excellent recreational opportunities, and a pleasant microclimate. In the canal-side locations near population centers, multipurpose trails including bike routes, pedestrian walkways and jogging paths can be developed on the lands that are already procured as the right-of-way on both sides of the canal (Fig. 6).

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Fig. 6. An example of canal-side development, Scottsdale, Arizona, USA. Pic by A. Adhikari

Through the improvements in irrigation, low-cost navigation, energy production, and hospitality industry, the canal system is expected to significantly boost Nepal’s economy and increase its gross domestic production (GDP).

Nepal is already a leader in micro-hydro and hydroelectric technologies in the mountainous terrain, and related management and knowledge. With the construction and operation of such a large canal system with multipurpose benefits, Nepal’s capacity in managing water resources will be enhanced creating leaders and experts in the field.

The need of New Laws and Policies

Since the water in the Grand Canal will flow between the provinces in Nepal, perhaps new water laws and policies, both at federal and provincial levels, need to be devised regarding water sharing and related rights and responsibilities. These internal water-sharing laws should be consistent with the bilateral agreements Nepal has signed with India. The plan for the Grand Canal also provides an opportunity to prepare guidelines for water use, rights and sharing within the communities, and how the groundwater recharge responsibilities and extraction rights and quotas are determined to ensure a sustainable water supply in the Nepali plains. Also, important are the implications of groundwater use and recharge across the border between India and Nepal as the aquifers can run underground across the national boundaries.

Conclusion

The ideas provided here are at a very high level of generality. The proposed canal and ancillary projects are not a panacea for all the developmental issues the country faces on many fronts. A project of this scale will also pose several challenges in financial, technical, social, legal, bi-lateral, and environmental fronts.

Nepali people and leaders have long believed that Nepal’s enormous water resources hold the key to the achievement of prosperity in Nepal. This proposal integrating water navigation, irrigation, energy generation, and recreational and tourism elements will be one of the major avenues to realize this potential.

Once this idea is of interest to the Nepali policymakers and political leaders, a pre-feasibility and subsequent feasibility analysis can address many of the technical, financial, social, and environmental issues that the proposed project may encounter. Any of the several international funding institutions may be able to help Nepal by providing grants to conduct the initial pre-feasibility and feasibility analyses.

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Dr. Ambika P. Adhikari is an Urban Planner and International Development Professional based in Phoenix, Arizona, USA. Dr. Keshav Bhattarai is a Professor of Geography at the University of Central Missouri, Warrensburg, Missouri, USA. Er. Om Raut is an internationally experienced Water Resources Engineer based in Nepal. Dr. Shiva Gautam is a Professor of Biostatistics at the University of Florida, Jacksonville, Florida, and USA.Dr. Keshab Sharma is a geotechnical engineer based in New Brunswick, Canada.

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