1 Introduction

Artificial watercourses are divided into various categories according to the purpose of the structure: irrigation, drainage, water supply, waterway, hydropower, wood industry, and simultaneously serving several purposes. Irrigation canals are hydrotechnical structures that transport water from the sources such as rivers and reservoirs to the irrigated areas. It may be lined or unlined, open, or piped. Irrigation water is an important resource for food security of inhabitants of Uzbekistan which is located in arid zone and member of user transboundary water resources (Sultonov and Pant 2023). At present, 75% of the irrigation canals in Uzbekistan is earthen, unlined, and as a result of natural processes such as vegetation, erosion, sedimentation and seepage, it can be observed that the current efficiency of the canal network is 63% (Arifjanov et al. 2022). Lining the canals to improve the water application efficiency is the major approach to adapt with the likely impacts of climate change in Uzbekistan.

Seepage losses from canals have been investigated by a number of researchers due to its importance. Review synthesized by (Lund et al. 2023) indicated that seepage from unlined canals ranges from 0.1 to 1 m3/day/m2. It is affected by factors such as properties of canal boundary soil, geometry, flow depth, velocity, level of groundwater, vegetation, and water properties. In some areas, depending on the regional conditions, infiltration can also have some positive effects by improving the groundwater resources (Singh 2022). On the other hand, if groundwater was polluted by long term irrigation agriculture, increasing groundwater level by canal seepage is donation for polluted streams (Abd-Elhamid et al. 2019). In irrigated area of Uzbekistan, which is located in Syrdarya basin, it was evaluated 54.9% weakly and 32.8% moderately saline irrigated areas and mineralization of groundwater was around 1.0 to 5.0 g/l (Khasanov et al. 2022).

The investigated canal in this study, Tashkent magistral canal (Tashkent MC), services irrigated farmland located in Chirchik-Okhangaran river basin which is considered a catchment area of Syrdarya. The theoretical and field investigation conducted by (Fatxulloev and Gafarova 2019) revealed that the average quantity of seepage lose from boundary of Tashkent MC is 1.37 m3/day/m2, and it varies according to the water depth. Also, the study indicated that hydrogeologic condition of trace effect on infiltration process. In another study, program developed by (Akhmedkhodjaeva and Khodjiev 2020) to calculate the efficiency of Tashkent MC. The results showed that, the efficiency was 0.78 with 0.012 difference compared to the natural case. Studies on Tashkent MC indicated that the decision makers must take urgent actions to adapt to the upcoming climate change challenges.

Covering the boundaries of the irrigation canal with materials such as concrete, asphalt, plastic, or clay is known as canal lining. However, the high cost of rehabilitation creates problems in the implementation of the process (Swamee et al. 2000). The canal size, hydrogeologic condition of trace, deformative or accumulative process occurs in the boundary of channel and rehabilitation budget are the main factors that help the decision makers to select the appropriate type of rehabilitation. Under the limited infiltration condition, and overestimated deformative process, the large irrigation canal can be partially lined, sides are lined, bottom is remained natural soil (Arifjanov et al. 2022). And this type of rehabilitation evaluated as a cost-effective method to improve the channel efficiency. However, if infiltration is not limited, lower efficiency like Tashkent MC, rehabilitation of canal requires completely lining to improve the water use efficiency in case of water scarcity.

Testing different lining material for different purposes has been investigated by modelling, laboratory experiments and field research. The two primary materials used for canals lining in Uzbekistan were geomembrane and concrete, both of which are widely employed in other countries for decreasing seepage losses and reduce contamination of groundwater resources. Modelling the seepage from polluted drains using geomembranes and concrete as a lining material reduced the extension of contaminants by 91.4 and 93% respectively compared with the natural condition (Abd-Elhamid et al. 2019). Numerical models used in irrigation canal revealed that concrete and geomembrane cause reduction of seepage 99 and 96% respectively, and utilized lining technique roles significantly impact of efficiency of lining material (Elkamhawy et al. 2021). In these cases, hydraulic conductivity of covering materials role the major factor for decreasing the seepage lose but the experimental study conducted by (Han et al. 2020) showed lower results under the influence of natural and artificial factors within some service time.

As a nonindustrial material, bentonite was used in some areas which has enough natural source. There are less than 10 bentonite deposits in Uzbekistan which has different properties (Maksimov 2012). Most of them are used in different industries like chemistry and medicine. Using bentonite as a lining material of irrigation channels was investigated recently in Uzbekistan by (Arifjanov et al. 2023). According to the laboratory experiments, using canal bed soil mixed with bentonite can reduce the seepage up to 80–90% when 4 kg bentonite is mixed with one square meter canal bed soil. Other experimental studies conducted in Egypt by (Elmashad 2018) showed that 8% bentonite mixed with sand has great impact of watertightness of canal boundaries.

One of the oldest methods which is not common currently is the asphalt lining. It was more common on repairing the waterway in 20 th centuries in the United States and Europe (Peters Ma and Brown Obe 2015). Study conducted by (Aboufoul and Garcia 2017) indicated that hydraulic conductivity of asphalt mixture is not only dependent on row material and layer thickness, but also depends on air void content. Also, the study revealed that the thickness of asphalt lining can be 5 to 15 centimetres depending on the canal size, and its hydraulic conductivity equals to less than 0.03 m3/day/m2, and it is the same for stone pitching.

Stone pitching, also called dry stone or boulder lining, is used for lining the earthen canal to increase its efficiency. Because of its high resistance to erosion, it is commonly used in hydrotechnical structures needed to protect erosion (Di Pietro and Mahajan 2022). There are two main world class mining industry corporation in Uzbekistan, called Navoi and Almalyk, which can be a source of stone for canal lining with their mining wastes. Stone mortared can provide the same service time with concrete lining if it is constructed and maintained properly (Ali et al. 2021).

According to the analysis of the literature, it was found that the water permeability of the lining materials in some cases lower than 50% or more than 0.1 m3/day/m2. However, quantity of water loses in canal depends not only on the material’s hydraulic conductivity, but also on the geometric dimensions of the canal boundary (Ghazaw 2011). One of the factors which affects the formation of the geometric dimensions of the canal is the resistance force between the flow and the boundaries, that is characterized by the roughness coefficient. According to (Hubert Chanson 2004), roughness coefficient of geomembrane, concrete, asphalt, sand mixed bentonite and stone pitching is equal to 0.011, 0.015, 0.017, 0.021, and 0.026 respectively. Depending on the roughness coefficient, the change of geometric dimensions affects the cost of canal construction.

The implementation of the research results focused on canal lining depends largely on the hydraulic properties and cost as well as lifetime of the lining material. Conforming to the Construction Act of Uzbekistan (No:02.06.03–2012) durability of geomembrane, concrete and asphalt lining is up to 8–10, 15–20, 7–10 years respectively. Stone pitching or boulder lining can serve around 20–25 years (Ali et al. 2021). Sand mixed bentonite has weak erosion resistant, so its durability is less than other materials, 3–5 years. But in any case, the lifetime of the lining material can vary depending on various factors such as the quality of row material, installation and exploitation conditions, and environmental factors (Han et al. 2020).

The aim of this study is to investigate how hydraulic characteristic of different lining materials affects the efficiency and rehabilitation costs of the Tashkent MC. There are a number of materials that can be applied to decrease the seepage loses from irrigation watercourses. In this work, we tested five materials; geomembrane, concrete, asphalt, sand mixed bentonite and stone pitching for the channel lining. Measurement works were carried out between Pk8 + 90 and Pk18 + 50 cross sections of the studied canal. During the field measurement, canal cross-sections and flow parameters were measured using the doppler, River Surveyor S5. HEC-RAS, hydrodynamic model, was used to analyse the effect of lining material on flow parameters.

2 Materials and Methods

The methodology used in this study includes a number of phases: field measurements for the hydraulic parameters of the study area, develop and calibrate the hydrodynamic model using HEC-RAS, study the effect of different lining materials on the hydraulic parameters of the canal, redesign and cost estimation of using different lining materials.

2.1 Description of the Study Area

Tashkent MC receives water from the Chirchik river through the Karasuv River and serves the irrigated areas of the Okhangaron River basin which is considered low-water basin (Fig. 1). The canal was built in 1940 with the help of the local inhabitants, and between 1958 and 1965, the canal was completely reconstructed. The canal receives water from 36 th km of the Karasuv river, the maximum capability in the starting part is 87 m3/sec, the total length of the canal is 62 km, and the canal consists of 7 reaches (Kadirov and Khasanov 2023).

Fig. 1
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Location map of the study area; source: own elaboration

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The magistral canal supplies irrigation water to 70,000 ha crop land which is located in both the Chirchik and Okhangaron river basins. In order to reduce the negative impact of the flow on the canal profile, the sides of the canal are lined with concret till cross-section PK 8 + 50, and other some part of the canal, from PK 8 + 50, begins to move throw natural bed. Canal hydraulic elements vary along its length, but in the first reach they are as in (Table 1).

Table 1 Design parameters of Tashkent MC, reach 1, from PK00 + 00 to PK42 + 00
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The technical condition of Tashkent MC was investigated by (Kadirov and Khasanov 2023) and showed that consequence of 60-year exploitation period, despite of the operational activities carried out in the canal, the efficiency of the canal has been decreased. The current efficiency of the canal is 79%, and this situation has a significant impact on the efficiency of using irrigation water in the basin. Analyzing the impact of hydraulic properties of different lining materials on economic efficiency of rehabilitation using hydrodynamic models reduces the economic obstacles in the construction. However, the use of hydrodynamic models requires reliable input data measured under natural conditions.

2.2 Field Measurements and Data Collection

The moving boat method was used to measure the hydraulic elements of the flow in the studied canal. Measurement device is the acoustic Doppler current profiler (ADCP River Surveyor S5), designed to measure the hydraulic parameters in a three-dimensional stream (see Fig. 2a) (Mardi and Murmu 2024). It is used for measuring water velocity, and commonly utilized in river and artificial channel. Device employs acoustic signals by emitting sound pulses at a specific frequency into the water, and then analysing the Doppler shift of the reflected signals. The velocity is calculated from the phase lag between two received acoustic signals that are transmitted with different energies and time intervals (Mardi and Murmu 2024). Moreover, the device can be integrated with GPS systems to provide precise positioning information for the collected geospatial data. There are many options to display data from measurement device, but we need the channel bathymetry, velocity distribution and boat trace to check quality of measurement (Fig. 2b). The bathymetric data allows natural reflection of the process in hydrodynamic modelling. Flow hydraulic elements determined by the device provide an opportunity to evaluate the efficiency of the model.

Fig. 2
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Tool of measurement, River Surveyor S5

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The field measurements were done at the first reach of the Tashkent MC. The distance, field research carried out is about one kilometre. Between two pickets, Pk8 + 90 and Pk18 + 50, five specific cross-section were chosen to obtain the hydraulic and bathymetric data. Average distance between the two cross-sections is 250 m despite distance between cross-section number 0 and 1. At every section, at least 4 and maximum 6 times measurements were carried out to supply accuracy and reliability of the field data. By analysing the measured data in each cross-section, one of them which has great accuracy according to indicator of standard division (Std Dev) was chosen for the hydrodynamic modelling (Fig. 3a and b).

Fig. 3
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View of cross sections profiles of Tashkent MC

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According to the measurement results, we can see that the water discharge in the canal during the measurement is 76.41 m3/s, the mean flow velocity is 0.95 m/s, the cross-sectional area is 80.91 m2, and the top width of the canal is 25.72 m (Table 2).

Table 2 Measured data
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According to analyzing the depth data, obtained there was no significant difference among the bathymetric characteristics of cross-sections (Fig. 4).

Fig. 4
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Cross section bathymetry of Tashkent MC

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2.3 Hydrodynamic Modelling

Studying and understanding the behaviour of water flow in irrigation canals allows engineers to make informed decisions and design efficient and effective water infrastructure projects. But there are some limitation and barriers to study the flow behaviour by conducting regularly research in the natural field conditions. In this point, modelling based on available and accurate measured data is an effective method for designing irrigation canals.

Designing an artificial-excavated-irrigation canal requires some simplifications and assumptions of the natural flow behavior, such as flow is steady, flow conditions are uniform. The one-dimensional energy equation, mostly common Bernoulli equation, is a fundamental equation used to describe the conservation of energy in the flowing water system (Hubert Chanson 2004).

$$\:{E}_{1}-{E}_{2}={h}_{e}$$
(1)

where: \(\:{E}_{1}\), \(\:{E}_{2}\) are total energy of each cross-section.

\(\:{h}_{e}\) is the energy loss mainly due to roughness of canal boundary.

There are several hydrodynamic software’s which have the capability of calculation of Bernoulli equation. Unlike other software’s, HEC-RAS is a software that is accessible and widely available for analyzing different scenarios such as lining material for open channels (Syarifudin et al. 2022). In this work, steady flow analyzing tool of HEC-RAS was used to analyze changes in the flow parameters when boundary material is changed. In this modelling approach, the flow is assumed to be one-dimensional, meaning that the velocity and depth of the flow only vary across the cross-section of the channel and are considered uniform along the longitudinal axis. But like other software’s reality of the result depends on the quality and the accuracy of the input data.

The 1-D steady flow analysis in HEC-RAS requires channel geometry, boundary conditions, and other relevant data to obtain accurate predictions of the water surface profiles, flow velocities, and other hydraulic parameters. In this research, bathymetric data obtained by field measurements (Fig. 4) is used as the geometric data, boundary condition assumes the flow continuous with normal depth and slope, other relevant data to check the accuracy of the model (calibration) is token from field data.

3 Results

The measured field data and the hydrodynamic model (HEC-RAC) are used for analyzing the effect of using different lining materials for irrigation channels on the efficiency and cost of canal reconstruction in Toshkent magistral canal, Uzbekistan. The model was calibrated and then used to assess different lining materials efficiency and the results are presented in the following sections.

3.1 Calibration of the Model

A geometric model of the study area was created using bathymetric data. The roughness coefficient of the canal bed was determined based on the literature, and longitude slope of canal was selected based on the design parameters of the channel (Fig. 5).

Fig. 5
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The geometry of Tashkent MC (reach 1) from Pk18 + 50 to Pk8 + 90

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According to the field data, the discharge during the measurement is 76.41 m3/sec. These data were entered as a flow parameter to the model. The boundary conditions considered that the flow continues in a steady-uniform conditions, and longitudinal slope is 0.00014. Based on the geometric data and the flow parameters, the model is calibrated and then used for simulating the effect of different lining materials on the canal efficiency (Fig. 6).

Fig. 6
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Model view of Tashkent MC in HEC-RAC

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To check the reliability of the hydrodynamic model, the correlation between the measured and the modeled flow areas at all the cross-sections from 0 to 4 was determined. According to the obtained result, the value of R2 equals to 0.86 (Fig. 7). Over 86% reliability of the model indicates that the model can be used in practice.

Fig. 7
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Model calibration: calculated vs. measured cross section area

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3.2 Analysing the Efficiency of Different Lining Materials

As a result of various technical measures performed in the canal bed against seepage, the roughness coefficient of the canal bed changes. This causes changs in the flow parameters. The practice of using concrete as a lining material is the most common in Uzbekistan (Fatxulloyev et al. 2023). However, using geomembrane, stone pitching, asphalt and even sand mixed with bethnonite can be used as lining materials. All of these materials are used as anti-filtration measures, but the priority of selection is determined by factors such as material efficiency (hydraulic conductivity), construction cost, and lifetime (duration of expluatation). Table 3 shows the properties of the used lining materials.

Table 3 Properties of lining materials
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As we can see, the exploitation duration of the geomembrane is very short, even if the hydraulic conductivity is good (very low). Sand mixed bentonite is more effective than the hydraulic conductivity of natural soil, but its duration of exploitation is not high enough. Concrete, stone pitching and asphalt have almost the same hydraulic conductivity and duration of exploitation. In such case, the economic efficiency of their construction is important.

Fig. 8
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The impact of roughness coefficient on the wetted perimeter

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The use of the above materials has different effects on the flow parameters because they have different roughness coefficients. Changes in the flow parameters cause changes in construction parameters and result in changes in the construction costs. According to hydrodynamic model results simulated by HEC-RAS, it can be seen that with the increase in roughness value of the lining material, the mean velocity of flow decreases, and the wetted area increases as shown in Figs. 8 and 9.

Fig. 9
figure 9

The impact of roughness coefficient on the mean velocity

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The ability to select a material for rehabilitation is improved if the flow parameters and canal construction parameters are considered when changing the lining material, as well as the cost of construction material in the local market.

3.3 Redesign and Cost Analysis of Canals Lined with Different Materials

The implementation of anti-filtration measures in canals requires a certain technological process. For example, before concreting the channel, its cross section should be brought to a certain prismatic state. In this study, we analys the economic effectiveness of anti-filtration measures for the first reach of Tashkent MC.

The element of special attention in the rehabilitation of canals is the water depth (h), and its change affects the discharge of the branches which receive water from the magistral canal. Therefore, it is important that its value remains unchanged after rehabilitation. The water discharge (Q), the longitudinal slope (s), and the side slope ratio (1/z) of the canal also remain unchanged. Under the influence of the lining material, the width of the canal bottom changes to maintain the specified water depth in the channel. At the same time, the values of the perimeter of the cross section of the channel are determined as the main element of the estimation of construction costs. In this study, the canal free board (a) and the thickness of layer (t) are determined based on existing construction act (No:02.06.03–2012) as shown in Table 4.

Table 4 Redesign parameters of Tashkent MC
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From the results shown in Table 4., we can see how lining material effects on channel boundary area. To keep water depth unchanged, bottom width increased according to the lining material roughness (Fig. 10). Stone pitching shows the largest value by 34.41 m2, while geomembrane has the smallest one.

Fig. 10
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Impact of lining material on channel boundaries

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According to the official Uzbekistan market prices, the cost of polymer geomembrane is average $2.85/m2 depending on its properties, average cost of concrete is $46.5/m3, sand mixed bentonite (30% bentonite) costs $22.54/m3, asphalt can be found for $47.5/m3, and stone pitching concrete consisted of $1.45/m2 calculated with 200 mm thickness stone and concrete. Calculation shows covering by stone pitching is the cheapest way to decrease seepage loses while the cost of concrete is the most expensive (Fig. 11).

Fig. 11
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Impact of roughness coefficient on the rehabilitation cost

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4 Discussion

Determining the canal construction parameters by evaluating the influence of the hydraulic properties of lining materials on the flow parameters is the base for the correct determination of the economic value of canals rehabilitation for decision makers. It was found that covering one RMT channel boundary surface with geomembrane, concrete, asphalt, sand mixed bentonite and stone pitching cost $61.87, $163.86, $127.63, $68.19 and $49.89 for raw materials expenses respectively. If the cost for these lining materials is calculated for the first reach of Tashkent MC, the cost increase dramatically to be $260, $688, $536, $286, and $210 thousand respectively. At this point, the lifetime of lining material play an important role. If the cost of raw materials divided into minimum lifetime of lining materials, geomembrane, concrete, and stone pitching shows the lowest annual expenses by $32, $46, $10 thousand respectively. According to the durability, experimental study conducted by (Han et al. 2020) reviled that forming of crack and hole over the surface geomembrane lining is much faster than concrete one, especially in seasonally frozen ground regions. On the other hand, using geomembrane and concrete require small channel cross sections, it means filler building materials like soil should be transported to the area. According to results of the current study, stone pitching showed almost the same cross section value compared to the natural case.

5 Conclusion

Watering is the main factor in obtaining sufficient yield in agricultural areas located in the arid zones. As an arteria of agriculture, irrigation canals serve as an important factor in the economic stability of Uzbekistan. To improve the water-use efficiency, the efficiency of irrigation canals must be improved. The quantity of seepage losses can be reduced by lining the irrigation canals. There are various lining materials which have been employed, but the priority of selection is dependent on some factors such as hydraulic properties, construction costs, and durability. Instead of durability, hydraulic properties (roughness) and construction cost affect each other. The roughness of the lining materials affects the channel geometry as well as the seepage rate and the construction costs. To analyses the effect of boundary material on water surface profile, the hydrodynamic model, HEC-RAC, was employed based on bathymetric data of Tashkent MC. The results show that when boundaries lined by geomembrane, channel hydraulic properties change dramatically. For example, the mean flow velocity increased from 0.95 to 1.70 m/sec, and other elements are changed respectively. However, when boundaries lined by stone, flow parameters remained almost unchanged. The wetted perimeter is the main parameter to calculate the amount of raw material required for rehabilitation. With different lining materials such as geomembrane, concrete, asphalt, sand mixed bentonite and stone pitching, it showed different values ranged from 21.69 to 34.41 RMT. By analysing the cost of raw materials, it is found that lining with geomembrane, concrete, asphalt, sand mixed bentonite and stone pitching for the first reach of Tashkent MC cost about $260, $688, $536, $286, and $210 thousand respectively. There is no significant difference among geomembrane, sand mixed bentonite and stone pitching, but in this moment the lifetime of the material plays an important role. Using stone pitching to reduces the seepage loses, it has more economical advantages. In the Tashkent region, there is the Almalyk Mining and Metallurgical Combine, which can be a good source of stone materials. Using mining wastes as stone pitching material can be more effective approach to improve the efficiency of Tashkent MC. This study could help the decision makers to select the best coating material based on the costs and durability. Moreover, lining the irrigation canals could increase its efficiency and enhance the water resources management and in turn affect the country economy.