Value Engineering Approach to Evaluate the Agricultural Drainage Water Management Strategies

Abstract

Excessive irrigating water that has not been adequately drained may cause more water to enter the crop root zone than is necessary. As a result, issues with increasing water table levels, waterlogging, and salinity get worse and cause crop productivity losses. Agricultural drainage water management strategies (ADWMS) can be used to protect the quality of groundwater, guarantee that crops have better moisture conditions, and provide irrigation water by reusing agricultural water drainage and using sub-irrigation practices. In order to decrease the effects of poor drainage, mitigate climate change, conserve the environment, and achieve food security, this study proposes a framework for choosing the most effective ADWMS in Egypt’s Nile Delta as well as the new lands. The value engineering approach is used to ensure the strategy’s functionality and to present some innovation in the process of developing alternative solutions that are financially evaluated using the life cycle cost technique. According to the study results, the most effective strategy (ADWMS-3) prioritizes improving drainage effectiveness, controlling groundwater table rise, and providing another irrigation water source while maintaining environmental protection. This strategy encompasses the use of a control drainage system, timing of fertilizer application, regulating groundwater table variation, and using sub-irrigation practices. ADWMS-3 achieves the highest values for the technical score of 8.06 and the value index of 18.59. This study advances the understanding of the topic by providing policymakers with a tool to (i) evaluate ADWMS and (ii) incorporate the added value and functionality into their policies regarding agricultural drainage water.

1. Introduction

Agricultural drainage is the process of removing excess water from the land to prevent the water table from naturally rising. The primary goals of agricultural drainage are to prevent waterlogging, control salinity and provide more agricultural land. Poor drainage can result in a variety of problems, including decreased crop yield [1]. Agricultural intensification may result in groundwater pollution due to the increased use of pesticides and fertilizers. Fertilizer containing nitrogen has been added to agricultural soils more frequently in recent years, which has intensified crop yield. However, the usage of nitrogen in quantities greater than what crops require has resulted in the introduction of nitrogen into aquatic environments, which today poses a threat to the biodiversity and health of ecosystems [2]. Groundwater quality has declined as a result of increased agricultural production and the careless application of pesticides and fertilizers. The overuse of pesticides and fertilizers enhanced chlorophyll activity and hastened the deterioration of the water’s quality in terms of nitrate concentrations [3]. Extra water and salts percolate far down if the soil drains freely and the groundwater table is not saturated [4,5]. As a result, groundwater pollution may increase [6]. Agricultural drainage systems are divided into two types: field and main systems. Surface drainage systems and subsurface drainage systems are terms used to differentiate field agricultural drainage systems that allow water to flow from the soil’s surface or beneath the soil’s surface. The primary drainage system consists of deep or shallow collectors, main drains, and disposal drains. Shallow collectors are used in surface field drainage systems but can also be used in pumped subsurface systems, whereas deep collectors are required in subsurface field drainage systems [7]. There have been numerous advancements in agricultural drainage systems, such as controlled drainage (CD) systems and ditch pond systems. Farmers implement control drainage by erecting water control structures at key drainage outputs. In order to control the water discharge from a drainage system, the amount of water at the drainage outlet is then managed. Essentially, CD allows the farmer to change the intensity of the drainage system based on farming needs at different times of the year, from full to partial to no drainage. Because it works by significantly lowering drainage volumes, CD promotes groundwater recharge, elevates the water table, and increases the availability of soil water in the root zone. These elements can reduce crop stress caused by water scarcity. Improved crop yield is caused by increased nutrient uptake, thus, increased fertilizer use efficiency [8]. Crop productivity has been shown to increase with CD increase. Corn and soybean yields can be increased by 10% on average. In some dry years, yields have increased by 20% [9].

Ditch-pond systems are another method of improving surface drainage. Ditch-pond systems can significantly reduce the negative effects of agricultural drainage on downstream canals and flood control in downstream areas. An off-line ditch-pond system can be used to effectively detain agricultural drainage water. As a result, when such a system is designed with an appropriate diversion weir, the impact of Agricultural drainage water management (ADWM) on downstream canals and areas can be significantly reduced [10]. Surface drainage has several negative effects on the environment. Drains covering is the utmost used method for attempting to reduce the environmental impacts that emerge around drains [11].

Agricultural drainage strategies are the procedures that allow for the natural or induced movement of excess water away from agricultural lands. Agricultural drainage strategies attempt to reduce groundwater levels, bring soil moisture down to field capacity, sustain the ideal soil moisture level for crops to grow effectively, and improve the soil structure because many soil structures collapse in extremely wet conditions [5]. Furthermore, the use of agricultural drainage strategies improves soil workability during planting and harvesting seasons, reduces the time required for the soil to dry out between crop seasons, and allows for the management of aquifer recharge potential in drained fields [12]. Agricultural drainage strategies are designed to ensure an abundance of adequate groundwater quantities. Groundwater is regarded as the most desirable renewable water resource for providing irrigation water for many agricultural lands due to its nearly universal availability and low investment costs [13].

Agricultural drainage strategies have progressed from being merely a means of removing excess water from soil profile to being a smart device that can be used to provide water to the root zone, when necessary, via what is known as “sub-irrigation methods.” As part of sub-irrigation techniques, water is injected back into the drainage system to raise groundwater levels and add moisture to the root zone [14]. Sub-irrigation is usually used in conjunction with controlled drainage or subsurface drainage. Sub-irrigation practices use at least half the amount of water and fertilizer used in conventional methods [15]. Continuous soil and irrigation water monitoring are critical, especially in cases of low water quality (reused agriculture drainage water and blending agriculture drainage wastewater with freshwater). Such analyses aid in identifying the soil salinity challenge so that remedial action can be initiated before it worsens. Field data on variations in irrigation water quality and soil salinity over time is also required when advising agricultural system adjustments that are equal to both water and soil salinity levels [16].

There is a gap in the literature concerning the use of ADWM techniques, such as developing strategies to effectively manage agricultural drainage water under various conditions, such as drainage water disposal, pollution, water scarcity, and food security, because drainage water management is a complex mixture of human activities, natural systems, and designed systems. The primary function of ADWM strategies is to dispose of drainage water while preserving groundwater quality and reusing drainage water to achieve the three goals of climate change adaptation, pollution reduction, and food security.

The goal of this study is to provide a framework for selecting the best ADWM strategy to use in Egypt’s new lands and the Nile Delta under a variety of conditions, such as poor drainage, climate change, food scarcity, environmental pollution, and water scarcity. This is accomplished by using the VE approach to develop several value alternatives for ADWM strategies and evaluate the value of these alternatives using LCC.

2. Methodology

The study’s goal will be achieved using the Value Engineering (VE) methodology as a problem-solving technique to generate several value alternatives for ADWM strategies and assess the value of various alternatives to ADWM strategies using the life cycle cost (LCC) approach. Using LCC, the cost and return of each ADWM strategy are combined into a single quantitative value.

VE is a multidisciplinary problem-solving approach that aims to increase the value of a product, process, or service by improving the functionality of each of its constituent parts. The VE approach’s goal is to execute the system’s fundamental function(s) at the lowest LCC while maintaining the required performance, safety, and effective quality. When the primary goal is to add value rather than cut costs, VE produces the best results. VE selects the best design option for each project. Real-world examples of value engineering showed that 10–20% reduction in project costs, indicating its utility [17]. In the field of water management, VE was used to find the best design solution for some of the most difficult irrigation issues, such as reducing the water deficit at the canals tail [18], selecting the best solution for drains covering [11], and modifying irrigation practices to mitigate climate change [19]. VE is also used to develop, evaluate, and analyze win–win transboundary water management strategies during the operating stage of the Grand Ethiopian Resistance Dam (GERD) [20].

When using VE to analyze ADWM strategies, there are five phases to go through [19]. The first phase is the information phase, during which the study’s objectives and the current state of the system are analyzed. The second phase, functional analysis, examines the current function of the system. The third phase is creativity, in which other methods that can achieve the main function of the agricultural drainage water system are proposed. The fourth phase is evaluation, which involves conducting a questionnaire survey to assess the proposed methods for managing agricultural drainage water based on key performance criteria. The last phase is development, in which the suggested methods are transformed into value alternatives, for which a technical score (TS) and a net present value (NPV) are calculated.

These value alternatives are evaluated based on assessment criteria collected from the literature. The weight of each assessment criterion is determined by a group of experts who give the score for each value alternative based on the extent to which each assessment criterion is achieved. Then, the TS is calculated by multiplying the score of the value alternative by the weight of the standard assessment criteria.

The NPVs for value alternatives are calculated using LCC analysis. LCC is a technique for calculating the overall cost of a system from conception through disposal. LCC is the sum of all expenses, both recurring and one-time, such as the purchase price, installation, start-up, operation, maintenance, and upgrade. Using net present value (NPV), LCC is used to evaluate different values. NPV is the difference between the current value of cash inflows and outflows. Equation (1) is used to determine NPV [21].

$$NPV=C_i+R_e-S_r+A_a+M+E$$

(1)

where: C_i: investment costs; R_e: replacement costs; S_r: resale value towards the end of its lifespan; A_a: annually recurring operating, maintenance, and repair costs; M: non-annually recurring operating, maintenance, and repair cost; E: energy costs.

Equation (2) is used to determine the Value Index (VI) by dividing the technical score (TS) by the total NPV.

$$Value Index \left(VI\right)=\frac{Technical Score \left(TS\right)}{Net Present Value \left(NPV\right)}$$

(2)

3. Results

3.1. Information Phase

The following elements are considered when evaluating the ADWM strategy: (i) reduce the negative effects of climate change and drainage on agriculture and the environment; (ii) improve ADWM to increase crop output and return on investment; and (iii) improve growers’ management skills, as well as identify how and where agricultural abstractors can participate in and support regional initiatives.

3.2. Function Analysis Phase

The main question asked during this phase is what are the basic functions of the agricultural drainage water system? Active Verb and Measurable Noun are two criteria used to describe each function. ADWM’s primary objectives are environmental conservation and food security. Crop yield enhancement, climate change adaptation, and agricultural drainage water management are all ancillary responsibilities.

The ADWM methods’ functions are defined using the Function Analysis System Techniques (FAST) diagram. The FAST diagram, as shown in Figure 1, is useful for quickly identifying goals and determining which resources are needed to enable economic growth, mitigate the negative effects of climate change, and ensure food security. The FAST diagram starts from the left by stating the higher order function of the ADWM system, then the basic function followed by non-basic functions are drawn from left to right with the logic that is based on asking the question “How” and ends at the far right by stating the lower order function of the ADWN system. The FAST diagram is validated by asking “Why” starting from right to left [19].

3.3. Creativity Phase

More innovative techniques are required to manage agricultural drainage water and reduce water stress. Water stress occurs when there is a greater demand for water than is available at any given time, especially when the quantity and quality of available water are declining. The question in this phase is, what other methods can achieve the main function of the agricultural drainage water system? In order to answer this question, a number of non-traditional ADWM strategies are generated, as shown in

Table 1. Proposed methods for ADWM strategies.

Code	Name	Description
M1	Surface ditch system	A method for draining excess water in humid flatlands with few hydraulic gradients, beneficial in agricultural lands with a low rate of infiltration and characterized by humidity [1].
M2	Dead furrow	A field’s final furrow, often created at the end of a field, somewhat wider than twice the width of a plough bottom [1].
M3	Tile drainage system	Perforated plastic tubing that is buried three to five feet underground. Water that isn’t attached to the soil is drawn out by the perforations. Not only does that reduce saturation, but when the water moves through, some of the oxygen gets integrated into the soil [1].
M4	Vertical drainage	Also known as well drainage, in which wells gather water through seepage and pump it out [22].
M5	Deep open drainage	Water collected by seepage. The drainage system needs to be deep enough to cross the water table [22].
M6	Control drainage system	The water discharge from a drainage system can be controlled by erecting water control structures at key drainage outputs. The drainage system’s intensity can be changed from full to partial to no drainage [23].
M7	Planting living mulch, winter cover crops, and perennial grasses	A fantastic, all-natural way to boost nutrients, enhance the texture of the soil, prevent erosion, and control weeds at the same time. They are sown from the end of summer to the beginning of autumn [24].
M8	Lowering the pace of fertilizer application	Aligning the nutrient supply with crop needs to maximize yields while reducing environmental losses [25].
M9	Time of fertilizer application	Application of fertilizer should be avoided on damp surfaces when rain is expected within the next 24 h [26].
M10	Evaporation basins	Using evaporation ponds to dispose of leftover drainage water [1].
M11	Source control	Irrigate fields more efficiently to apply less water, which will use less drainage water [27].
M12	Connection of scattered ponds with drainage ditches	Minimize the peak flow, temporarily store some of the water from a drainage area and lessen the effects of agricultural drainage on drainage canals and downstream locations [24].
M13	Regulating groundwater table variation	A stronger prediction map and ability to capture the trend with seasonal fluctuation may result from adding more piezometric wells with higher resolution data over a longer period [22].
M14	Drainage water reuse	Water is collected from various drainage sources, treated, and then used once again to irrigate plants that can tolerate salt better, like cotton, eucalyptus, energy crops and feed crops [22].
M15	Reduction in drainage water	Lower the size of the area planted with high-water-use crops [25].
M16	Covering of main drains	A closed watercourse is used to prevent solid and liquid waste from being dumped into the drains and harming the environment [11].
M17	Planting salinity tolerant crops	The majority of the major grain crops have good salt tolerance. Sorghum, wheat, triticale, ripe, oats, and barley are included in this category. Rice and corn are the only exceptions [28].
M18	Using sub-irrigation practices	To boost the moisture in the root zone and raise groundwater tables, water is pumped back into the drainage system [14].
M19	Rehabilitation of the current subsurface drainage system	To keep the design elements of the drains clean, remove all types of weeds from the drains and wash all the subsurface drainage networks that have been installed to ensure good performance by clearing any obstructions in the network [10].
M20	Leaching requirements	What is the total amount of water needed to reduce the soil salinity from a high beginning value to one that is appropriate for the crops being produced and within their salt tolerance [1]?

.

3.4. Evaluation Phase

A questionnaire survey was undertaken to evaluate the proposed methods for managing agricultural drainage water and to eliminate those responses deemed unrealistic or ineffective. The three factors that determined whether an expert was qualified to participate in the questionnaire survey were as follows: (1) comprehension of the value engineering methodology, (2) competence in agricultural drainage water management, and (3) profound understanding of the effects of climate change. The survey questionnaire was sent to 106 Egyptian experts who met the eligibility requirements. The questionnaire survey received 39 expert responses, resulting in a 36.8% response rate.

According to the demographic profile of the respondents, 25.6%, 59.0%, and 15.4% had less than five years, between five and ten years, and more than ten years of experience, respectively. The respondents were project managers (23.1%), drainage engineering professionals (48.7%), and water engineers (28.2%), respectively.

The experts were asked to rate the twenty proposed agricultural drainage water management methods based on five performance criteria, including positive environmental impact, increased crop productivity, water table rise control, excess water removal efficiency, and positive impact on groundwater quality. The performance criteria were rated on a 5-point Likert scale, with 1 denoting poor performance and 5 denoting excellent performance [22].

Twenty methods for managing agricultural drainage water were presented to the experts for review. Figure 2a–e show the average score for each criterion for each method. Figure 2f displays the overall score for each method. The acceptance/rejection threshold is set at a neutral final score of 2.5 points. As a result, four methods, M₂, M₄, M₅, and M₁₀, were rejected, while the remaining sixteen methods were qualified to proceed to the VE development stage.

3.5. Development Phase

The goal of this stage is to transform the suggested methods for managing agricultural drainage water into value alternatives (strategies). These strategies will be covered in the part that follows, along with how to pick the best one.

3.5.1. Value Alternatives (ADWM Strategies)

Six agricultural drainage water management strategies (ADWMS) are developed from 16 approved methods.

ADWMS-1

The first strategy focuses on enhancing the existing drainage system, reducing peak flow, reducing the impact of agricultural runoff on drainage canals, increasing soil organic matter, decreasing nitrogen leaching, suppressing weeds and pests, improving soil productivity, and protecting the environment from pollution. This strategy combines four methods: the surface ditch system (M₁), planting living mulch, winter cover crops, and perennial grasses (M₇), the connection of scattered ponds with drainage ditches (M₁₂), and rehabilitation of the current subsurface drainage system (M₁₉).

A surface drainage system collects and discharges water from an area by using ditches or channels. This method is utilized on low-permeable-soil fields. Cover crops can be used to control weed growth by directly competing with weeds for resources such as sunlight, water, and soil nutrients. Cover crops are plants that cover the soil and can be used to increase soil organic matter, reduce nitrogen leaching, inhibit weeds and pests, and boost soil productivity. Winter cover crops are planted immediately before or shortly after the main grain crop is harvested, and they are eliminated before or shortly after the next grain crop is planted. Oats, winter wheat, barley, triticale, and winter rye are examples of small grains that make excellent winter cover crops since they can withstand light frost and are often inexpensive to sow. Crop yield improved by 25% when cereal rye-containing cover crops were left in place for a longer period [29]. Using drainage engineering techniques coupled with ditches and ponds can reduce climate change-related drainage damage from flooding by more than 25% [7].

ADWMS-2

The second strategy prioritizes environmental protection while utilizing current drainage techniques and de-salting the soil. This strategy incorporates using a surface ditch system (M₁), lowering the pace of fertilizer application (M₈), reduction in drainage water (M₁₅), and leaching requirements (M₂₀).

Increasing the efficacy of surface irrigation may reduce drainage water and surface drainage challenges. Improving irrigation efficiency will reduce percolation and improve drainage. Lining irrigation channels improves irrigation efficiency and saves 30–40% of water [30]. Crop productivity and quality are considerably improved by organic fertilizers, but if they were applied improperly, they might pose a serious environmental issue, such as nitrate pollution [26]. In order to avoid salt buildup in the root zone during repeated cycles of irrigation and evapotranspiration, the obvious solution is to apply water in an amount greater than evapotranspiration. This will intentionally cause a portion of the applied water to flow through the root zone and flush away the excess salts. To stop salt stress and decrease salt deposition in the active root zone. Leaching is necessary to remove the salts from the soil, and the leaching requirement is 12.7% from irrigation water [31].

ADWMS-3

The third strategy prioritizes improving drainage effectiveness, controlling groundwater table rise, and providing another irrigation water source while maintaining environmental protection. This strategy encompasses using of control drainage system (M₆), time of fertilizer application (M₉), regulating groundwater table variation (M₁₃), and using sub-irrigation practices (M₁₈).

The groundwater table is highly controlled by the use of a control drainage system. By raising the control structure level after the application of nutrients or by completely blocking the drainage outlet to prevent any drainage from the soil, it is possible to reduce nutrient losses. Control drainage systems provide high-quality groundwater and ensure higher agricultural output as well as better quality for nearby water bodies [24].

Application of fertilizer should be avoided on damp surfaces when rain is anticipated within the next 24 h to maximize crop benefits, minimize increased fertilizer discharge on drains, and prevent the degradation of drainage water. The ideal solution is to apply fertilizer two days after a significant downpour [27].

The rising groundwater table has an impact on crop yield. The rise in the groundwater table might reduce agricultural yield by 37% [23]. Sustainable management practices include regulating groundwater table fluctuation based on an extensive groundwater monitoring network to predict groundwater level using geostatistical methods applied to a precise collection of data to identify sensitive locations and regulate the rise in the water table.

Using techniques such as sub-irrigation, a smart tool for irrigating the root zone as required, the drainage water might be used for irrigation. Water is injected back into the drainage system using these techniques to increase the moisture content of the root zone and raise groundwater levels [14]. Sub-irrigation practices complement controlled drainage or tile drainage. The use of water and fertilizer is at least 50% lower when these approaches are used than when conventional methods are used [15].

ADWMS-4

The fourth strategy emphasizes better drainage water management through improved drainage and irrigation system efficiency, using drainage water as an irrigation water resource, conservation of groundwater quality, and reduce environmental contamination. This strategy includes using of tile drainage system (M₃), lowering the pace of fertilizer application (M₈), source control (M₁₁), and using sub-irrigation practices (M₁₈).

In order to provide enough air space within the soil, tile drainage drains surplus sub-surface water from fields. The water table is efficiently reduced by laying tile drainage, allowing plants’ roots to grow appropriately. Because the soil is not saturated with water, oxygen can still be found in the soil pores and used by roots. A correctly constructed tile system can enhance crop yields by 5% to 15% [23].

Artificial intelligence and smart irrigation networks, which improve irrigation efficiency and reduce drainage water, can be used to control the source of drainage water. A smart irrigation system’s essential part is a microcontroller, which serves as the system’s brain. After analyzing the sensor’s data on moisture content, decisions are taken regarding whether to water the area. When the soil is dry, water flows freely into the field, but when the soil is moist, the flow ceases. In the end, this process guarantees that the field’s moisture content and water availability are maintained at an appropriate level [28].

ADWMS-5

The fifth strategy focuses on employing an efficient drainage system, locating additional irrigation supplies, choosing an appropriate crop pattern, and protecting the environment. This strategy consists of using a tile drainage system (M₃), drainage water reuse (M₁₄), covering main drains (M₁₆), and planting salinity-tolerant crops (M₁₇).

One potential source of irrigation water is the recycling of agricultural drainage water. Agricultural drainage water is frequently recycled in dry or semi-arid areas when irrigation water is scarce. In reuse systems, irrigation water of higher quality is automatically combined with drainage water. The amount of drainage water that can be recycled depends on the quantity and quality of both irrigation and drainage fluids. Under certain circumstances, drainage water can be used for sustainable aquifer management as well as an extra source of irrigation [32]. In situations when the drainage water is of reasonable quality, conventional agriculture will probably reuse it. Where water is either marginally or extensively salinized, only salt-tolerant plants may be able to use it [23]. When using recycled drainage water, crop output can be increased by planting salinity-tolerant cultivars of energy crops, such as Jojuba and palm, which are the best alternatives for being irrigated by saline water [33].

Agricultural drains must be covered to decrease the negative impacts of open drains, especially those that are adjacent to residential areas, and to use the land space the drains take up for a road or another use. Drain coverings are helpful in controlling seepage, reducing organic and inorganic pollutants, assisting with relocation, reducing disease ecology, pests, and aquatic weeds, and increasing the monetary value of surrounding properties by 64.5% [11].

ADWMS-6

To better manage agricultural drainage water, the sixth strategy focuses on increasing drainage system efficiency, boosting nutrients, improving the texture of the soil, preventing erosion, controlling weeds, predicting the level of the groundwater table, and providing an additional source of irrigation water. This strategy includes using of control drainage system (M₆), planting living mulch, winter cover crops, and perennial grasses (M₇), regulating groundwater table variation(M₁₃), and drainage water reuse (M₁₄).

3.5.2. ADWMS Assessment Criteria

Each of the six value alternatives is evaluated using ten assessment criteria. These assessment criteria were taken from the literature. A scale from 0 to 5, where 0 indicates no relevance of a criterion and 5 indicates the significance of the criterion over the other, is used to express the relevance of each evaluation criterion with respect to the others. The format of the questionnaire is shown as a comparison matrix in

Table 2. Assessment Criteria Weighting Matrix.

Assessment Criteria		A	B	C	D	E	F	G	H	I	J
Minimizing the duration of the soil’s saturation [1]	A		* B-3	** A-3	D-2	E-2	F-3	G-2	A-2	A-3	J-2
Suitable for the environmental issues that population growth and climate change bring [19]	B			B-3	B-2	E-3	B-2	B-2	B-3	I-2	B-2
Make their water removal systems and infrastructure more durable [6]	C				D-3	E-2	F-2	G-3	H-2	I-3	C-2
The expectations of the farmers and their capacity to pay [1]	D					D-2	F-2	D-1	D-3	I-3	J-2
Improving of cooperation between the water sector and other sectors [19]	E						F-3	G-4	H-2	I-3	J-2
Supportive of the environment [8]	F							G-3	F-3	F-2	F-3
Health and safety [19]	G								G-3	I-2	G-2
Easy to construct [19]	H									I-3	J-3
Water saving [20]	I										I-2
Reducing nutrient losses via drainage flux [23]	J

Notes: * criteria “B” is more important than criteria “A” with a score of 3 out of a maximum of 5. ** criteria “A” is more important than criteria “C” with a score of 3 out of a maximum of 5.

. The ADWMS assessment criteria comparison matrix was filled out by the same expert panel that had previously evaluated the proposed methods. The questionnaire received 33 responses from experts. The relative weights (W) of the assessment criteria, as computed by averaging the responses of the experts, are displayed in Figure 3c.

3.5.3. ADWMS Scoring

The same study expert panel was requested to score the value alternatives (strategies) based on the assessment criteria as they filled out the assessment matrix. On a scale of 0 to 10, the panel was asked to rank each technique in relation to each assessment criterion. A score of 0 denotes the alternative’s least significant relevance in the evaluation criteria, while a score of 10 denotes the alternative’s most significant significance in the evaluation criteria.

The average expert scores are presented in Figure 3a. The average strategy scores of all experts for each criterion in Figure 3a are multiplied by the weights of the criterion in Figure 3c to create the weighted score in Figure 3b. The Technical Score (TS), which indicates that ADWMS-3 has the highest technical score, is computed by adding together all the weighted values for the assessment criteria for each strategy indicated in Figure 3d. The Value Index (VI) is then calculated using Life Cycle Cost (LCC) to identify the best value alternative.

3.5.4. LCC Analysis

To evaluate which ADWMS is most effective, the six proposed ADWMS are applied to a study area in Egypt as an example of nations suffering from a variety of challenges. Egypt’s reliance on conventional drainage methods has resulted in several problems, including a rise in salinity and waterlogging, a decline in crop yields, and environmental contamination. The crop cost and income are calculated for the crop yield, which is cultivated per square meter of the study area. The six ADWMS expenses and income are calculated over a 30-year period. Based on Egypt’s prices for 2022, each ADWMS’s expenses and income are computed. Equation (3) is used to determine the NPV of each ADWMS.

$$NP{V}_{S j}=\sum PV{r}_k-PV{c}_k\left\{\begin{array}{c}for j=1, k=1, 7, 12,19\\ for j=2, k=1, 8, 15,20\\ for j=3, k=6, 9, 13,18\\ for j=4, k=3, 8, 11,18\\ for j=5, k=3, 14, 16,17\\ for j=6, k=6, 7, 13,14\end{array}\right\}$$

(3)

where NPV; the net present value of the strategy, s; agricultural drainage water management strategy (ADWMS), PVr; the present value of the method revenue, PVc; the present value of the method cost, j; code of the strategy, and k; code of the method.

Equation (4) is used to convert the future value to the present value, while Equation (5) is used to convert the annual value to the present value [30].

$$PV=\frac{F}{{\left(1+i\right)}^n}$$

(4)

$$PV=A\frac{{\left(1+i\right)}^n-1}{i*{\left(1+i\right)}^n}$$

(5)

where PV; present value, F; future value, i; discount rate, n; number of years, and A; annual value.

PV for the initial systems costs, revenue, and NPV of each method utilized within ADWM strategies are shown in Figure 4 and Figure 5.

The detailed LCC analysis, including expenses and revenues for methods M₁, M₃, M₆, M₇, M₈, M₉, M₁₁, and M₁₂, are presented in Figure 4a–h, respectively. Similarly, the detailed LCC analysis for methods M₁₃, M₁₄, M₁₅, M₁₆, M₁₇, M₁₈, M₁₉, and M₂₀ are presented in Figure 5a–h, respectively.

To elaborate the PV calculations, Figure 4a presents the PV of the surface ditch system (M₁) system initial cost, operation, and maintenance (O&M), crop cost, and crop revenue is 0.31, 0.03, 0.072, and 0.565 $/m², respectively. Figure 4a also shows that the NPV of M₁ equals 0.153 $/m².

Each ADWMS consists of four methods, as introduced in Equation (3). The present value of strategy cost (PVc), the present value of strategy revenue (PVr), and the net present value for all six ADWMS are shown in Figure 6.

3.5.5. ADWMS Evaluation

As shown in Figure 7, Equation (2) is used to determine the Value Index (VI) for each ADWMS by dividing the technical score (TS) over the total NPV. As TS rises, the value of the alternative rises. ADWMS-3, which encourages more adaptable collaborative strategies to achieve the triple goals of environmental conservation, food security, and climate change adaptation and mitigation, has the best value, as demonstrated by the calculations in Figure 7. The highest value of TS and VI are for ADWMS-3, which indicates that this is the best strategy.

4. Discussion

ADWMS-3 has been identified as the optimal strategy based on the preceding results. ADWMS-3 focuses on improving drainage efficiency, lowering groundwater table rise, and providing a new source of irrigation water while protecting the environment. Utilizing a control drainage system (M₆), timing the application of fertilizer (M₉), regulating groundwater table variance (M₁₃), and sub-irrigation practices (M₁₈) are the four methods included in this strategy.

ADWMS-3 uses the control drainage system to tightly regulate the groundwater table, hence minimizing nutrient losses. There is a minimal possibility that it will contaminate surrounding water bodies. Controlled drainage may be a useful management approach to reduce hydrologic nitrate exported from crop fields without raising concerns about major pollutant swaps or increased greenhouse gas emissions from the soil surface [34]. Application of fertilizer two days after a large downpour is required to maximize crop benefits, reduce increased fertilizer discharge on drains, and limit the degradation of drainage water [2,26].

Building a vast groundwater monitoring network to forecast groundwater levels and pinpoint sensitive locations is how the water table rise is managed. The drainage water could be used as a source of irrigation water by employing sub-irrigation methods. Sub-irrigation is a technique that can be used to raise groundwater levels and the moisture content of the root zone by injecting water into the drainage system [19]. The use of a hydrometeorological forecasting system in conjunction with automatic water level control structures is strongly recommended to create an integrated water management system [35]. Consequently, ADWMS-3 is regarded as the most effective method for managing agricultural drainage water and achieving the objectives of environmental protection and food security.

Although previous studies presented methods to manage drainage water, they did not consider the LCC of the proposed methods or combine different methods to formulate an overall strategy. This was achieved in this study by adopting LCC analysis and combining multiple methods to formulate a comprehensive strategy to manage agricultural drainage water. The findings of this study should be interpreted within the context of the limited study area and the subjective evaluation of alternatives based on expert judgment.

5. Conclusions

This study introduced a methodology to manage drainage water in Egypt’s new lands and the Nile Delta by merging several methods into multiple agricultural drainage water management strategies (ADWMS). This strategy was accomplished by developing numerous value alternatives for ADWM strategies using the value engineering (VE) technique and evaluating these alternatives using life cycle cost (LCC). The principal study results are:

• VE offers a novel way to compare the ADWMS as “value alternatives” that have been proposed to identify the most functional alternative. The goal of VE is to find “the best value,” or the perfect equilibrium between merit and cost.
• LCC analysis captured the overall cost of each alternative method from inception to disposal, which is highly recommended in comparing different methods rather than focusing solely on the system’s initial cost.
• Despite large differences in PVr and PVc across the six ADWMS, all of them have a fairly near NPV.
• ADWMS-3 is the optimal strategy for managing agricultural drainage water to achieve the required goals, with a TS of 8.06 and a VI of 18.59.
• ADWMS-3 includes using the following four methods: utilizing a control drainage system (M₆), timing the application of fertilizer (M₉), regulating groundwater table variance (M₁₃), and sub-irrigation practices (M₁₈).
• ADWMS-3 slightly higher VI is mostly affected by the evaluation of the experts more than the NPV.
• The study’s findings emphasized the utility of using problem-solving methodologies, such as VE, in producing realistic, easy-to-implement solutions to water management challenges.
• The study’s conclusions should be viewed within the context of the study’s limited scope and the subjective evaluation of alternatives based on expert judgment. Further extension of this study may attempt to use an objective evaluation of strategies to eliminate the human bias from the process.