Surveying for Construction of Irrigation Projects

Surveying for Irrigation Projects

Surveying is the first step in constructing an irrigation project such as dams, barrages or weirs. This is done to evaluate the need for the construction of any irrigation structures, and to determine if the region will benefit from them. This allows engineers to make an informed decision as to whether an irrigation project is necessary and appropriate. The survey helps them assess the topography of the area, the availability of water resources and the local climate, to ensure that the project will be beneficial for the region.

Surveying for Construction of Irrigation Projects

The steps involved in surveying to build an irrigation structure are

1. Examine the water availability
2. Examine the topography
3. Selection of site
4. River gauging
5. Marking of CCM
6. Marking of tentative alignment
7. Reconnaissance survey
8. Preliminary survey
9. Final location survey
10. Final Survey Report

Examine Availability of Water

Establishing the Water Availability

When constructing an irrigation project, the first step involves establishing the water availability. This can be done by examining the type of river in the area, whether it is a perennial or inundation type. Additionally, the river should meet the requirements of the local area in terms of water supply.

Identifying a Suitable Site

Once the water availability has been established, the next step involves determining a suitable site for the construction of the irrigation project. Factors such as topography, soil type, and presence of any other infrastructure should be taken into consideration when identifying a suitable site.

Examining the Project Requirements

The final step in the construction of an irrigation project is to examine the project requirements. This includes assessing the type of project that needs to be constructed, such as a dam, weir or barrage, and the materials required for the project. Additionally, any other special requirements such as permits and environmental assessments should be taken into consideration.

Examine Topography

Investigating Water Availability

When planning for an irrigation project, it is important to consider the water availability of the area. This includes analyzing the topography map of the area, examining the behavior of agricultural lands, and evaluating the water sources that can be used for irrigation. By doing this, it is possible to identify the resources that will be needed for the project, as well as the potential alignment for the project.

Analyzing the Topography Map

The topography map of the area is a key part of understanding the water availability. This map gives a detailed overview of the land features, and can be used to identify potential sources of water, as well as the most suitable alignment for the irrigation project. By studying the topography map, it is possible to gain a greater understanding of the natural environment, and to plan the project accordingly.

Examining Agricultural Lands

When planning an irrigation project, it is important to consider the behavior of agricultural lands. This includes analyzing the soil type, drainage, and potential sources of water. By doing this, it is possible to identify any areas that may be too dry or too wet, and to ensure that the irrigation project is designed to meet the needs of the agricultural lands.

Selection of Construction Site

SITE SELECTION FOR IRRIGATION PROJECT

When a large source of water is available, the selection of a suitable site for the construction of an irrigation project such as a dam, barrage or weir is critical. The selection process should consider a variety of factors, including the soil survey, basin size, access to materials and labor, allowable bed slope, and the potential for submerging valuable lands or areas.

SOIL SURVEY

A soil survey is essential in order to determine the depth of foundation required for the irrigation project. This is conducted by boring and pile testing.

SUFFICIENT BASIN AREA

The basin size must be sufficient to meet the demand for the project. It should also be checked to ensure that it is not too large, as this could lead to flooding or other problems.

ACCESSIBILITY

The site should be easily accessible to ensure that materials and labor can be readily sourced.

ALLOWABLE BED SLOPE

The allowable bed slope should be maintained as far as possible in the canal in order to reduce the risk of erosion.

SUBMERGING VALUABLE LANDS

The structure should not submerge valuable lands and areas, as this could cause environmental damage or destruction of important resources.

River Gauging

Calculating River Discharge

River gauging is the process of measuring the amount of water that passes through a particular point in a river. The point is selected for a specific project and the discharge is calculated on a daily basis and the yearly records are studied.

Recording HFL and LWL

High Flood Level (HFL) and Lowest Water Level (LWL) are also recorded based on the observations from previous years. This helps in understanding the variability of the water level in a river over time.

Silt Analysis of River Bed

Silt analysis is conducted to find out the possible silting of the river bed. The amount of fine silt present in the river is measured to find out the manorial value of the silt. This helps in understanding the potential impact of the silt on the environment.

Marking of CCM

What is Cultivable Command Area (CCA)?

Cultivable Command Area (CCA) is a geographical area which is suitable for growing crops and other agricultural activities. It is usually identified and demarcated on topographic maps and is used to determine the potential yield of a particular agricultural area. It is important to note that the construction of any projects should not disturb or damage the CCA.

How CCA is Useful?

The CCA is a useful tool for determining the required discharge for any agricultural project. It provides information on the land that is suitable for agriculture and the potential yield that can be obtained from the area. This helps to ensure that the project is not damaging the environment and that it is providing an adequate amount of water for the agricultural activities. The CCA also helps to determine the areas that are prone to flooding and other natural hazards.

Why is it Important to Preserve CCA?

It is important to preserve the CCA as this ensures that the agricultural activities are not disturbed or damaged. This also helps to ensure that the project is not damaging the environment and that it is providing an adequate amount of water for the agricultural activities. The CCA also helps to identify areas that are prone to flooding and other natural hazards. This helps to reduce the risk of damage to agricultural land and ensures that the project is providing an adequate amount of water for the agricultural activities.

Marking of Tentative Alignment

1. Alignment Selection to Maximize Cost-Effectiveness:
   After the selection of site for irrigation structure, it is time to select the tentative alignments for canals or branch canals. These alignments should be marked in topographical and contour maps. The alignment marked should cover the whole area when it is cut into canal, while also minimizing the earth filling and cutting costs.
2. Considerations When Choosing Alignment:
   When choosing the alignment, it is important to take into consideration the impact of the alignment on the surrounding environment. This includes avoiding valuable agricultural lands, religious places, etc. It is also important to ensure that the alignment crosses rivers, roads, rails etc. perpendicularly.
3. Summary:
   The selection of alignment for an irrigation structure is an important consideration in the planning process. The alignment should cover the whole area when cut into a canal, while minimizing the costs of earth filling and cutting. It is also important to consider the environmental impact of the alignment and ensure that it crosses rivers, roads, rails, etc. perpendicularly.

Reconnaissance Survey of Irrigation Projects

Reconnaissance Survey for Alignments

A reconnaissance survey is conducted to gather key details regarding tentative alignments for a project. This survey helps to determine the nature of the ground slope, magnetic bearings of lines, any religious places or valuable lands that may be crossed, and other important factors. The survey also notes distances, records any past floods, and identifies suitable cross drainage works. Any rivers that are crossed should be done so at the shortest possible width.

Nature of Ground Slope

The nature of the ground slope along the alignment is noted during the reconnaissance survey. This helps to determine the feasibility of the alignment and plan any necessary safety measures.

Magnetic Bearings of Lines

The magnetic bearings of the lines of the traverse along the alignment are measured and recorded during the reconnaissance survey. This helps to ensure that the alignment is properly aligned and to check the accuracy of the measurements taken.

Religious Places and Valuable Lands

If the alignment passes through any religious places or valuable lands, these areas are eliminated. If they are unavoidable, they are marked as special areas and suitable compensation is provided.

Nature of Ground

The nature of the ground up to a distance of 100m on both sides of the alignment are also recorded. This helps to identify any potential hazards that may be present and to plan accordingly.

Crossings Perpendicularly

Any alignments that cut crossings perpendicularly are also noted. This ensures that the crossings are properly aligned and that the alignment is safe to navigate.

Measuring Distances

Distances are measured by pacing during the reconnaissance survey. This helps to ensure that the alignment is accurate and properly aligned.

Past Flood Records

The past records of floods in the area are also noted during the reconnaissance survey. This helps to identify any potential flood risks and plan accordingly.

Cross Drainage Works

The reconnaissance survey also looks for any suitable cross drainage works. This helps to ensure that the area is properly drained and the alignment is safe to navigate.

Rivers Across Alignment

If there is any river across the alignment, the alignment should cut the river across its shortest width. This helps to ensure that the alignment is properly aligned and that the river is not crossed at a dangerous width.

Preliminary Survey of Irrigation Projects

Preliminary Survey Steps:
The first step in the preliminary survey for an irrigation project is the construction of pillars on both banks of the river to mark the center line of the project. Boring is then done along the center line to determine the depth of the foundation. A permanent benchmark is then created and its value is connected to the nearby GTS benchmark by fly leveling. Plane table survey or prismatic survey is then conducted up to a distance of 100m on both sides of the alignment and a route survey map is prepared.

Longitudinal and Cross Leveling:
Longitudinal leveling is then conducted with an interval of 20m, while cross leveling is conducted with an interval of 100m. Permanent bench marks are then arranged along the alignment with some interval gap.

Studying Water Table and Soil:
The water table level is studied on both sides of the alignment up to a distance of 200m. The soil along the alignment is also surveyed.

Cross Drainage Works and River Crossings:
The details of road and railway crossings are noted to design cross drainage works. At river crossings, the cross section details of river are noted and the cross sections of the river are taken on both upstream and downstream sides with a covering of 500m distance.

Drawings and Estimate Sheets:
Drawings are then prepared for all the maps and cross sections. Estimate sheets are also prepared for earth works, compensations for lands etc.

Final Location Survey

Steps Involved in Final Location Survey

The final location survey is conducted to determine the most economical alignment among all the options. This survey involves the following steps:

1. Marking Center Line of Final Alignment:
   The center line of the final alignment is marked with pillars and pegs. This helps to determine the exact position of the alignment.
2. Marking Width of Alignment:
   The width of the alignment is also marked with pillars. This helps to determine the exact width of the alignment and to ensure that the required width is maintained throughout.
3. Marking Branch Canal:
   Similarly, the pillars are also marked for the branch canal. This helps to determine the exact location of the branch canal and to ensure that all required parameters are met.
4. Recording Final Eligible Properties for Compensation:
   Lastly, the final eligible properties for compensation are recorded. This helps to determine the total amount of compensation that needs to be provided to the affected owners.

Final Survey Report of Irrigation Project

Final Stage of Irrigation Project: Report Preparation
The last stage of an irrigation project is the preparation of a report with the details of the final alignment. This report is then submitted to the relevant authorities to seek approval for the project. It is important to provide a comprehensive report that outlines the necessity, justification and benefits of the project, as well as a detailed estimate of the earth works, compensation, head works and other related costs involved. The report should also include various maps and drawings, such as a general map of the area through which the canal passes, route survey map, longitudinal section of alignment, cross section of alignment and contour map of alignment, as well as drawings of the dam, head works, cross drainage works etc.