Investigating On-Site Energy Consumption Patterns Using Vertical Electrical Sounding (VES) and Geographic Information System (GIS) Techniques

Abstract

In recent decades, the fortunes of energy economies have been closely linked in Pakistan. A major energy inefficiency issue was found in Pakistan due to the mismatch between horsepower (HP) requirements and bore depth. Keeping this in view, a total of 194 tubewells were chosen for an energy audit in the Multan region, Pakistan. The Terrameter SAS 4000 was used to measure the accurate demand of the head during the resistivity surveys at all of the selected locations. The results showed that the tubewell sets were installed arbitrarily at high power, irrespective of the provided flow and head, and these pumps used more energy for their flow. The results revealed that the efficiency of the tubewell sets increased from 35 to 54%, from 55 to 80%, from 49 to 80%, and from 48 to 75% for centrifugal pumps with electric motors and diesel engines and for turbines with electric motors and diesel engines, respectively. A weighted overlay analysis indicated that the efficiency of tubewells covering 838.12, 1131.8, and 2077.1 km² for centrifugal pumps with electric motors, diesel engines, and turbines, respectively, was enhanced for the study area. Similarly, the energy saved for the study area covered 1423.8, 1161.1, and 1131.1 km², as shown by the overlay analysis. The results revealed that the annual energy saving was found of 3486 kw for 194 tubewells, resulted in the saving of USD 0.204 million in operational costs over one year. The overall results indicate the strong need to adopt proper investigations of the head and power requirements before installing a system in the study area.

1. Introduction

Agriculture is important for the growth and sustainability of Pakistan’s economy. It has become a prominent industry, accounting for around 19.2% of the country’s gross domestic product (GDP), and it is responsible for the provision of employment for 39% of the workforce. Cotton, sugarcane, wheat, maize, and rice account for about 23% of the total agricultural production and 4.32% of the GDP. Agriculture in Pakistan provides livelihoods to more than 65–70% of the population [1]. Irrigation water is a crucial input for agricultural production and is regarded as the backbone of all agricultural operations [2]. Irrigation water in Pakistan is derived from rainwater, surface water, and groundwater. However, the Indus River System is the main source that provides surface water for agricultural purposes [3]. Rivers draw water from the mountains as a result of melting glaciers, melting snow, and flowing monsoon rains. In India and Pakistan, the Indus Basin Irrigation System (IBIS) covers a total area of 26.02 mha (million hectares). Out of 26.02 mha, about 22.14 mha stretches over Pakistan [4]. The Indus Basin Irrigation System, as the largest gravity flow irrigation system, comprises three reservoirs and a total of 16 barrages. Apart from these, across the main rivers, there are two head works and siphons, along with 12 link canals, 45 main canals, and about 150,000 watercourses. The canal’s total length is 34,834 miles, with a culturable command area (CCA) of approximately 16 million hectares (Mha) [5].

Recently, the contribution of agriculture towards Pakistan’s GDP has reduced because of the increased population rate and the shifting of the agricultural land [6,7]. The dominance of cereals, grains, and other crops has reduced over the years, leading to a shortage in per capita food availability [8]. The leading cause of this situation is the scarcity of areas with sufficient water supplies to fulfil crops’ water requirements [9]. In Pakistan, about 75% of the total available surface water is diverted into the canal network, and only 34% of it is received by farms [10]. This leaves 40 to 60% of the water requirements for the crops to be met by groundwater sources. As a result, the available surface water and precipitation are insufficient to fulfil the present demand for water for agricultural purposes [11]. Groundwater is the most reliable source and is being used worldwide for irrigation, domestic, drinking, commercial, and industrial purposes. However, the most common use of groundwater is for drinking purposes [12,13]. In addition, the use of groundwater increases crop yields by 150–200% and increases crop intensity by 70–150%. As a result, the number of tubewells in the country has been increasing over the years to meet the irrigation water requirements [14].

Pakistan has one of the best canal irrigation systems in the world, but there is still a shortage of water throughout the country. The annual average rainfall is less than the overall crop water demand, so the canal water and rainwater amounts are insufficient to meet the irrigation needs of the agricultural sector. To tackle the water scarcity problem, the country has installed more than one million tubewells, of which the majority are diesel-operated, and around 0.13 million agriculture pumps in the Punjab region are connected to an electric grid [15,16]. In Pakistan, water shortages are a huge challenge. At the same time, the inefficiency of the irrigation system not only leads to the wastage of water resources but also increases energy consumption when running tubewells [17,18].

Tubewells in Pakistan are powered by 2–25-horsepower electric motors or 12–25-horsepower diesel engines, with an annual energy budget of PKR 6040 million and PKR 12,294 million, respectively [19,20]. Moreover, the pumping systems are installed and used in the field without prior investigation, resulting in energy losses that affect the farmers’ economic conditions [21]. The main reason for the energy losses is the imbalance of the required and installed systems in the farms. Moreover, installing the pump head without analyzing the head requirements can also result in high energy consumption [22]. Currently, the farming community is unaware of or has less access to investigations of the groundwater resources and the pumping units required for farming operations. There is a large gap to address, and to search for solutions that assist farmers to reduce their input costs for irrigation [23,24,25] and to counter such scenarios in the field, there is a need for a prior investigation of the pre auditing and post auditing efficiencies, power requirements concerning the pumping of groundwater under existing motor pump set arrangements, and retrofit measures for improving tubewells’ efficiency [26,27]. Keeping this in view, the present study was carried out to provide useful information to the farmers of the Multan district in the province of Punjab, Pakistan to determine the correct head to be installed to achieve the maximum tubewell efficiency. A spatial distributional analysis was performed for all of the tubewell parameters. An overlay analysis for the tubewell efficiency parameters was conducted to differentiate the existing installed system from the system that needs to be installed for a specific area.

2. Materials and Methods

2.1. Study Area

The research study was conducted within the Multan district that spans from 71°22′ E to 29°56′ N. The district Multan is surrounded by Khanewal towards the northern side, Lodhran towards the southern side, Vehari towards the eastern side, and the Chenab River towards the western side (Figure 1). The Chenab River serves as a primary source for surface and groundwater recharge in the region. The Multan district is renowned for its major crops such as wheat, maize, sugarcane, cotton, rice, sunflower and other fodder crops. Additionally, minor crops like mustard, mung bean, mush bean, lentil, chickpea, and rapeseed are also cultivated in the Multan district. The reason for selecting the Multan district as the study area was the non-availability of river water in the southern side of the district, leading to the installation of tubewells for crop irrigation.

2.2. Data Collection

In collaboration with Agricultural Engineering Workshops (Field Wing) in the Multan division of Punjab, Pakistan, a total of 194 sampling locations were selected for comprehensive auditing of the tubewells. Data pertaining to available head, discharge, efficiency, and energy consumption for each tubewell were diligently gathered from these sampling locations. Throughout the area, tubewells were categorized into four operational configurations: centrifugal pump with an electric motor, centrifugal pump with a diesel engine, turbine with an electric motor, and turbine with a diesel engine. The distribution of tubewell sets based on these arrangements is shown in

Table 1. Arrangement of tubewell sets in Multan district.

Sr No.	Arrangement Type	No. of Installed Tubewells (N)
1	Centrifugal + Electric Motor	106
2	Centrifugal + Diesel Engine	67
3	Turbine + Electric Motor	12
4	Turbine + Diesel Engine	9

.

2.3. Data Interpretation

During the tubewell auditing, the operational performance of tubewells in the study area were checked and analyzed, focusing on parameters such as power consumption, discharge, head, and overall efficiency. The trajectory method was employed to measure tubewell discharge, while a power analyzer was utilized to estimate power consumption. Head was measured through resistivity survey using Terrameter SAS (Signal Averaging System) 4000. A series of measurements for earth resistivity survey was made by increasing the electrode spacing in each successive step around a fixed point. After the evaluation of available total dynamic head (T.D.H.), the pump efficiency and motor efficiency were determined using the following equations:

$$\mathrm{Pump} \mathrm{efficiency} \left(\%\right)=\frac{\left(\mathrm{Flow} \times \mathrm{T}.\mathrm{D}.\mathrm{H} \times 9.81\right)\times 100}{3600 \times \mathrm{Avg}. \mathrm{Input} \left(\mathrm{KW}\right)}$$

(1)

$$\mathrm{Motor} \mathrm{Efficiency}=(\mathrm{A}+\mathrm{B} \times \mathrm{Motor} \mathrm{Power} \mathrm{Factor})+(\mathrm{C} \times \mathrm{Current} \mathrm{Imbalance})$$

(2)

$$\mathrm{Current} \mathrm{Imbalance}=\frac{\left|\mathrm{I}1-\mathrm{I}2\right|+\left|\mathrm{I}2-\mathrm{I}3\right|+\left|\mathrm{I}3-\mathrm{I}1\right|}{\mathrm{I}1+\mathrm{I}2+\mathrm{I}3}$$

(3)

In this context, T.D.H represents the total dynamic head, and the variables A, B, and C signify the motor rating constants. After the audit, a calculation was made for the replacement of the existing motor with a new and low horsepower motor aligned with appropriate motor pump set sizing. This adjustment was proposed to achieve a higher discharge with minimal energy consumption.

2.4. Pump System Sizing

The sizing of pump systems was identified using the standard pump characteristic curve used by [28,29] rather than relying on a mathematical model. These curves determined the relationship between efficiency, head, power and flow. The primary purpose for this evaluation was to determine the current system’s operation flow and total head requirements. The optimal pump system was selected by applying the system flow requirements with different pump characteristic curves. Based on the selected pump, a motor with a rated capacity of at least 20% greater than the pump horsepower (Hp) requirement was selected. After proper sizing and modification, the efficiency of the pumping system was determined for both the pre audit and post audit phases to examine improvement in tubewell efficiency and reductions in energy consumption.

2.5. Spatial Distribution Maps

Spatial distribution maps were created to investigate the spatial variability of discharge, head, horsepower, and overall efficiency using ArcGIS version 10.7. These maps were prepared for the tubewell arrangements involving a centrifugal pump with an electric motor, and a centrifugal pump with a diesel engine. However, in the case of turbines, both arrangements (turbine with electric motor and turbine with diesel engine) were combined to form a single map due to the availability of fewer data points. The GPS receiver was used to obtain the location of the sampling site while performing vertical electrical soundings (VESs) for head calculation. The technique of ordinary kriging was used to create spatial distribution maps for all of the parameters of the aquifer. Ordinary kriging is a geostatistical approach used for interpolating a random variable at an unknown location based on its value at a neighboring place [16]. The data were log-transformed before employing the ordinary kriging interpolation technique to correspond the essential assumptions for ordinary kriging. The histogram and normal Q-Q plot were created in SPSS software 28.1.10 package using the log-transformed data to test the normality of the data and confirm that they conformed to the normal distribution. According to the literature, kriging is the best interpolation technique and has numerous benefits over the others [30]. The spatial distributions for all of the parameters were analyzed through these maps. However, a weighted overlay analysis was performed using ArcGIS 10.7 to compare the actual efficiency with the predicted efficiency, and to compare energy consumption with energy saving.

3. Results and Discussion

3.1. Summary of Energy Audit

The primary reason for energy losses is the mismatch of the required and installed systems on farms. The installation of pump heads without a thorough analysis of the head requirements result in high energy consumption [22]. Prior to the installation of the tubewells, all of the groundwater parameters including the quantity and quality should be considered. There is a strong need to address and to achieve such solutions to assist farmers in reducing their input costs of irrigation [23,24,25]. To counter such scenarios in the field, there is a prior need for an investigation of the pre auditing and post auditing of efficiency, a power requirement concerning the pumping of groundwater under existing motor pump set arrangements, and retrofit measures for improving the tubewell efficiency [26,27].

Table 2. Summary of the tubewell audit in Multan district.

Parameters	Pump Arrangement
	Centrifugal(E.M)	Centrifugal(D.E)	Turbine(E.M)	Turbine(D.E)
HeadActual (m)	27	20	27.19	34.11
HeadPredicted (m)	11.46	9.05	11.39	13.34
H.PActual	30	45	29	61
H.PPredicted	14	13	15	23
DischargeActual (m3/s)	0.028	0.029	0.036	0.038
DischargePredicted (m3/s)	0.067	0.079	0.077	0.080
EfficiencyActual (%)	22.37	48.11	36.97	50.93
EfficiencyPredicted (%)	45	69.23	73	66.05
No. of Tubewells (N)	106	67	12	9

(E.M): Electric Motor, (D.E): Diesel Engine, (H.P): Horsepower.

presents the summary of the complete tubewell audit taken out in the Multan district. The summary was taken out of the parameters like the actual and predicted head (m), power (horsepower, hp), discharge (m³/s), and efficiency (%). All of the values were determined as an average of each parameter. The summary of the auditing shows that the installation of the tubewell set has a higher consumption of energy, and a smaller energy supply can be used for all four types of tubewell arrangements. It was observed that previously, tubewell sets were operating with an efficiency ranging from 22 to 50% against a discharge of 0.028–0.038 m³/s. After the auditing, the overall working efficiency improved to 45–73% against the discharge of 0.067 to 0.080 m³/s. It was also observed that the tubewell sets were operating at very high levels of power consumption, but the auditing revealed that the power consumption can be reduced. The minimum power consumption before the auditing was 30 hp, and the maximum was 61 hp. However, the post auditing indicated that the average minimum power consumption was 13 hp, and the maximum power consumption was 23 hp. These results indicated that there was a huge loss of power, resulting in a high operational cost.

3.2. Improvement of Centrifugal_(E.M)

Improvements in efficiency and energy consumption were observed after the auditing of the tubewells (centrifugal + electrical motor), when the existing discharge, head, power, efficiency, and energy consumption were compared with the predicted discharge, head, power, efficiency, and energy saving, as shown in Figure 2a–e.

For all of the parameters of the tubewell in the auditing, mismanagement was observed regarding the selection of a pumping system before the installation. It was observed that the existing tubewell sets were consuming 24 to 40 hp in the study area. However, 7.5 to 26 hp was required to run the system, as revealed by the auditing of the tubewells. This excessive use of power resulted in a higher consumption of energy during the operational hours of the tubewell. It was observed that the amount of consumed energy was more than that of the required energy. This was due to the imbalance requirements of power against the installed boring depth [31]. The results also indicated that the auditing of the existing tubewell sets not only handles the power requirement but also decreases the energy consumption, optimizes the discharge of the tubewell set, and enhances efficiency by up to 54%, as shown in Figure 2a–e.

3.3. Improvement of Centrifugal_(D.E)

Improvements in efficiency and energy consumption were observed (Figure 3a–e) when the pump operating parameters such as the head, discharge, power, efficiency, and energy consumption were compared during the pre auditing and post auditing of the tubewells (centrifugal pump + diesel engine).

The results revealed a similar pattern of mismanagement while deciding the tubewell set specifications for a centrifugal pump running with a diesel engine, as observed in the case of a centrifugal pump with an electric motor. The tubewell sets were installed with systems with higher power consumption levels, where the need to operate the systems was quite less. The results indicated that the average head requirement was 10 m, while the installed tubewell sets were observed on an average head of 20 m. This resulted in less discharge of the tubewell sets, where a discharge of 0.029 m³/s was observed for the diesel engine arrangement. However, after the audit of the tubewell sets, the discharge was optimized from 0.029 to 0.079 m³/s. It was also observed that the installed tubewell sets were consuming 18 to 75 hp. The auditing of the tubewell sets recommends that the power supply to the tubewell sets should lie between 6.6 and 39 hp. The auditing for this type of arrangement also optimized the discharge of the tubewells with an enhanced efficiency of about 80% (Figure 3a–e). This will not only reduce the operational hours but will also result in less energy consumption while running a tubewell system.

3.4. Improvement of Turbine_(E.M)

Figure 4a–e represent the auditing of the turbine running with the electric motor for the parameters of the head, discharge, power, efficiency, and energy requirement. Most farmers of the study area used tubewell sets in combination with a centrifugal pump with an electric motor and diesel engine. Very few users were observed to have turbines with diesel engines and electric motors. Most of the installed tubewell sets were observed working improperly against the head requirements due to the unfit installation of the tubewell sets. At the head of 29 m for this arrangement, an average discharge of 0.036 m³/s was obtained. However, the audit of the tubewell sets recommended an average head of 15 m, which can enhance the average discharge from 0.036 m³/s to 0.079 m³/s.

In this case of tubewell arrangement, the installed power system with 25 to 40 hp was replaced with a system consuming 6 to 24 horsepower. This decrease in power consumption was observed due to the selection of right-sized pumps using the pump characteristic curve. The overall working efficiency of the already installed tubewell set was from 25 to 49%, and it improved from 63 to 80%. This increase in overall efficiency not only ensured higher discharge values compared to the pre auditing phase but also ensured higher values of energy savings in the study area (Figure 4a–e).

3.5. Improvement of Turbine_(D.E)

Figure 5a,b indicate the results of the tubewell auditing for a turbine pump running with a diesel engine. The selected parameters were like the other three pump arrangements. A mismatch was also observed among the pump system selection and desired borehole depth in this case of pump arrangements. It was observed that the already installed systems were operating at a higher pumping head against the lower pumping head requirement in the study area. The higher use of a pumping head was responsible for the higher energy consumption of the tubewell during the operational hours.

The results indicated that the turbine pump running with a diesel engine was consuming more energy during its operational hours. This higher consumption of energy was due to the imbalance between the higher selected head and power. The power consumption levels for the existing tubewell sets were observed to be from 55 to 65 hp. However, the comprehensive auditing resulted in a reduction in this power consumption, ranging from 6 to 45 hp. This huge difference in power consumption before the auditing of the tubewells resulted in higher operational costs in the study area.

It was also observed that the discharge available before the auditing phase ranged from 0.026 m³/s to 0.065 m³/s (cumec). However, after the auditing of the tubewells, this discharge was optimized from 0.045 m³/s to 0.112 m³/s, which also reduced the available head from 6.62 m to 20 m. The available head before the auditing of the tubewell sets ranged from 28 to 38 m. The results also indicated that the previous overall working efficiency of the tubewell sets was in the range of 38 to 55%. After the auditing of the tubewells, the working efficiency improved from 48 to 75%. This resulted in less energy consumption of the turbine tubewell sets running with a diesel engine. Spatial distribution maps were developed and used to analyze the spatial pattern using the field data because this is an easy and more accurate method than other analytical methods.

3.6. Spatial Distribution Maps of Discharge

The spatial distribution maps of discharge were prepared for post tubewell auditing using ArcGIS10.1. These maps were prepared for the tubewell arrangement of a centrifugal pump with an electric motor, a centrifugal pump with a diesel engine, and for turbines. To prepare the maps for the turbines, the data for both the arrangements with an electric motor and diesel engine were combined because very few locations were observed using turbines for pumping purposes. Most of the farmers were connected to centrifugal pumps with electric motors. The spatial distribution maps of discharge for the post auditing of tubewells are shown in Figure 6. The results indicated that the maximum discharge was achieved after the auditing was conducted towards the upper boundary of the study area in the northeastern side and the lower boundary in the southeastern side of the study area in the case of a centrifugal pump with an electric motor. The values of discharge in these areas ranged from 0.065 m³/s to 0.175 m³/s. However, most of the study area was observed to have discharge values ranging from 0.019 to 0.064 m³/s. A lower discharge was observed towards the southwestern side up to 0.018 m³/s, as shown in Figure 6a. In the case of a centrifugal pump with a diesel engine, the upper boundary was observed with higher discharge from 0.065 to 0.159 m³/s, while lower discharge values of up to 0.018 m³/s were observed in the central part and lower boundary towards the western side. In the case of turbines, most parts of the study area were observed with higher discharge values in the upper boundary and lower boundary, but some traces with less discharge were observed in the central part of the study area.

3.7. Spatial Distribution Maps of Head

The spatial distribution maps of head for the post auditing of the tubewell are shown in Figure 7. The results indicated that the uppermost boundary and the central part of the study area were observed with less available head after the post auditing of the centrifugal pump with an electric motor. It was also observed that the lower boundary towards the western side indicated a high available head that ranged from 61 to 80 m, as shown in Figure 7a. On the other hand, in case of centrifugal pumps with diesel engines, the uppermost area towards the western side and central part were observed with less head compared to the lower boundary on the southern side, where the observed head was higher, as shown in Figure 7b. Similarly, in the case of turbines, most of the area after the auditing was observed with less available head from the upper boundary towards the central part of the study area. The overall results indicated that the depth of the borehole should be selected up to 40 m where the system consumes less energy, resulting in good efficiency for all types of pump arrangements.

3.8. Spatial Distribution Maps of Power

The spatial distribution maps of power for the post auditing of tubewells are shown in Figure 8. The results indicated that after the post auditing of the tubewell sets, the power consumption was reduced in the study area. The results indicated that in the case of a centrifugal pump operating with an electric motor, the power consumption was lower in the northeastern part and the central part of the study area. The power consumption values in these parts of the study area were observed to be up to 20 hp. Moreover, the uppermost boundary towards the northern side and the portion from the center of the study area towards the western side were observed to be in the moderate range of power requirement. The power requirement values in these parts of the study area were found to be 21 to 40 hp, while the lower boundary indicated a power requirement of 41 to 60 hp, as shown in Figure 8a. On the other hand, in the case of a centrifugal pump operating with a diesel engine, the northeastern side and the center part towards the western side were observed with smaller power consumption values of up to 20 hp. The southwestern side indicated that the power consumption of the tubewell sets ranged from 21 to 40 hp, while the upper boundary indicated a higher power consumption of 41 to 60 hp in the study area, as shown in Figure 8b. Similarly, the auditing of the turbines indicated that the lower power requirement in the study area extended from the upper boundary towards the center of the study area. The lower boundary towards the southwestern side indicated that the power consumption of the tubewell sets should be in the range of 21 to 40 hp (Figure 8c).

3.9. Spatial Distribution Maps of Efficiency

The spatial distribution maps of the overall improved efficiency for the post auditing of tubewells were prepared in ArcGIS 10.1 (Figure 9). The results indicated that before the auditing, the tubewell sets were operating at much lower efficiencies and at much higher energy consumption levels. The sole reason behind this was the improper management of power and the head. The results indicated that after the auditing, higher operating efficiencies, ranging from 71 to 80%, of the tubewell sets (centrifugal pump with electric motor) were observed in the eastern and western boundaries of the study area. The upper boundary on the northern side was observed with 61 to 70% efficiency, while the lower boundary indicated much less efficient areas for pumping (Figure 9a). Similarly, in the case of a centrifugal pump with a diesel engine and turbine, a maximum efficiency ranging from 61% to 70% was observed in the southwestern side and the central part of the study area.

3.10. Overlay Analysis of Centrifugal_(E.M)

The weighted overlay analysis of a centrifugal pump operating with an electric motor is shown in Figure 10. The overlay analysis was performed to assess the improvements made after the tubewell auditing. The overlay analysis was carried out to discuss the factors related to the pumping systems, i.e., the overall efficiency and the energy savings. Many researchers have used a GIS-based weighted overlay analysis to analyze, handle, and manage spatially related information [32,33,34]. The weightage during the analysis was adjusted at a 50/50 influence for the pre audit and post audit of the tubewell. The results indicated that the efficiencies of the tubewell sets were optimized from poor to higher values after the tubewell audit. Of the total area of 3770 km² for the Multan district, only 30.8 km² was observed with poor efficiency, while the overall area showed an optimized efficiency of the tubewell sets (Figure 10a). A total of 2900.6 km² was observed with moderate efficiency, and 838.12 km² showed good efficiency of the system. Similarly, the energy savings improved overall, except for the central and western sides. The study area was divided into three categories based on energy saving, including low (327.8 km²), moderate (2017.9 km²), and high (1423 km²).

3.11. Overlay Analysis of Centrifugal_(D.E)

The overlay analysis for the centrifugal pump operating with a diesel engine is shown in Figure 11. Just like the centrifugal pump (E.M), two factors (overall efficiency and energy savings) were considered for the analysis. The weightage influence was also 50/50 for both the pre audit and post audit of the tubewell. The results indicated that the efficiency of the tubewell sets improved very effectively throughout the study area. The tubewell sets working with minimum efficiency were replaced with the systems with maximum efficiency. Only some of the traces towards the western side and the southern side were observed with tubewell sets with lower efficiencies (Figure 11a). The maximum efficiency was observed in the western and central parts of the study area. The results also indicated that the area with a lower efficiency ratio covered only 201.8 km². The areas with the maximum efficiency and moderate efficiency covered 1131.8 km² and 2435.9 km², respectively. Similarly, most of the energy saving was observed in the northeastern side and western side of the study area. The central part and western side showed smaller ratios of energy saving that covered 825.26 km², while the remaining area of 1782.7 km² showed moderate energy saving (Figure 11b).

3.12. Overlay Analysis of Turbine

The weighted overlay analysis for the tubewell auditing is shown in Figure 12. The analysis for the turbine was carried out by combining both the arrangements for the electric motor and diesel engine because of the smaller availability of turbines working in the study area. The factors considered for the turbine were like those considered for the centrifugal pump with an electric motor and diesel engine. The weightage influence was kept at 50/50 for the pre and post audit of the tubewell. The results indicated that the efficiency of the turbines were enhanced to such a level, whereas no traces of lower efficiency of the system were observed. The overall area showed moderate and good ranges of efficiency. Most of the area indicated maximum efficiency towards the northwestern and lower boundaries of the study area. The covered area was observed for both, and the ranges were 2077.1 and 1692.5 km², respectively, as shown in Figure 12a. Similarly, energy saving was enhanced for the pumping system across the study area, as shown in Figure 12b. The results indicated that energy saving was lower in the upper boundary. Energy saving was observed to be in a moderate range in the northeastern zone of the study area. The maximum energy saving was observed in the center and western sides of the study area.

4. Conclusions

Higher energy consumption may lead to higher production costs and a decrease in crop yield. Therefore, energy conservation/the installation of energy-efficient tubewells may save 3486 KW of energy and USD 0.204 M in operational costs annually for 194 tubewells, which will finally increase the net return. The country’s energy sector will face various challenges, including inefficiencies in energy production and distribution. Immediate steps should be taken to secure energy and overcome these challenges and to ensure sustainable economic growth. The inefficient use of energy and inadequate maintenance are two of the primary reasons for high energy demand. This will result in high prices, frequent power outages, and a negative impact on the environment. A total of 194 locations were selected in the Multan district to audit, analyze, and compare the performance and efficiency of the existing tubewells in the study area. The comprehensive auditing of the tubewell sets was conducted to suggest the retrofit measure that can optimize the efficiency of the working tubewell sets with a maximum discharge and less energy consumption. The comparison of pre auditing and post auditing was carried out, and spatial distribution maps were developed for this purpose, which concluded the following results:

• The comprehensive results indicated the need for the auditing of tubewell sets in an effective and efficient way to analyze the performance of the existing tubewell sets. There is a prior need for an investigation before installing a system to pump the water out from the aquifer.
• The spatial analysis proved to be helpful to decide on and recommend system requirements based on the audit of the existing tubewell sets. Based on the results, the maximum head should be kept towards the northwestern, center, and northern sides of the study area for Centrifugal_(E.M), Centrifugal_(D.E), and turbine, respectively.
• The efficiencies of the tubewell sets were enhanced after the post auditing phase. The overall efficiencies for Centrifugal_(E.M), Centrifugal_(D.E), Turbine_(E.M), and Turbine_(D.E) improved from 35 to 54%, 55 to 80%, 49 to 80%, and 48 to 75%, respectively.
• The auditing of the tubewell suggests that the actual head requirements and selection of the right pump size for the system result in higher discharge from the systems.
• The weighted overlay analysis for the overall efficiency of the tubewell indicated that the maximum area with a higher efficiency was observed in the northeastern side and western side of the study area for all types of tubewell arrangements. Similarly, energy saving was also observed to be higher in the northeastern side and western side of the study area after the auditing of the existing tubewell sets.

The detailed results of the tubewell auditing showed an annual energy saving of 3486 kw, which resulted in savings of USD 0.204 million in operational costs in one year.