Abstract: The main objective of this research was to compare different irrigation methods based on a parametric evaluation system in an area of 3011.9 ha in the Miheh plain of the Chahar Mahal and Bakhtyari Province, in the center of Iran. After analyzing and evaluating the soil properties, suitability maps were generated for surface, drip and sprinkler irrigation using Geographic Information System (GIS). The results showed that 73 ha (2.42%) of the lands in the studied region is highly suitable for surface irrigation. Whereas, 1355.8 ha (45.01%) and 907.6 ha (30.13%) of the study area are highly suitable for drip and sprinkler irrigations, respectively. Also, by applying drip and sprinkler irrigations instead of surface irrigation method, land suitability classes of 2848 ha (94.56%) of this plain will improve. The main limiting factors in using both drip and sprinkler irrigation methods in this area were soil texture, slope and the calcium carbonate content and the main limiting factor in using surface irrigation methods were slope and soil texture. The results showed that drip and sprinkler irrigation systems are the most suitable for Miheh plain (except the lands of 4.1 soil series), compared to the surface irrigation.
INTRODUCTION
Security and stability of food in the world rests on the management of natural resources. Due to the reduction of water resources and an increase in population, the extent of irrigated area per capita is declining and irrigated lands now produce 40% of the food supply (Hargreaves and Mekley, 1998). According to FAO methodology (FAO, 1976) land suitability is strongly related to “land qualities” including erosion resistance, water availability and flood hazards which are derived from slope angle and length, rainfall and soil texture. Sys et al. (1991) suggested a parametric evaluation system for irrigation methods which was primarily based on physical and chemical soil properties. Factors affecting the soil suitability for irrigation are: physical properties such as permeability and available water content, chemical properties such as soil salinity, alkalinity and acidity, drainage properties such as depth of ground water and environmental factors such as slope. The capability index for irrigation (CI) is calculated based on the multiplied by above factors.
Bienvenue et al. (2003) evaluated the land suitability for surface (gravity) and drip (localized) irrigation in the Thies, Senegal, by using the parametric evaluation systems. Regarding surface irrigation, there was no area classified as highly suitable (S1). Only 20.24% of the study area proved suitable (S2, 7.73%) or slightly suitable (S3, 12.51%). Most of the study area (57.66%) was classified as unsuitable (N2). The limiting factor to this kind of land use was mainly the soil drainage status and texture that was mostly sandy while surface irrigation generally requires heavier soils. For drip irrigation, a good portion (45.25%) of the area was suitable (S2) while 25.03% was classified as highly suitable (S1) and only a small portion was relatively suitable (Nl, 5.83%) or unsuitable (N2, 5.83%). They showed the limiting factors for surface irrigation as drainage and soil texture of the region. Also, they specified the soil depth, soil texture with coarse gravel and/or poor drainage.
Mbodj et al. (2004) examined the suitability of lands for two methods of surface and drip irrigation in the north of Tunisia, using the parametric method. The results showed that the suitability of drip irrigation is more than surface irrigation because of topography (slope), soil limitations (depth and texture) and drainage. Dengiz (2006) investigated the different methods of irrigation (surface, drip and local) based on the parametric evaluation in the pilot fields of Ikizce central research institute, located in south of Ankara, Turkey and concluded that the drip irrigation resulted in the increase of suitability of the lands by 38% compared to the surface irrigation.
Albaji et al. (2008) carried out a land suitability evaluation for surface and drip Irrigation in the Shavoor Plain, in Iran. The results showed that 41% of the area was suitable for surface irrigation; 50% of the area was highly recommend for drip irrigation and the rest of the area was not considered suitable for either irrigation method due to soil salinity and drainage problem. Albaji et al. (2010a) compared the suitability of land for surface and drip irrigation methods according to a parametric evaluation system in the plains west of the city of Shush, in the southwest Iran. The results indicated that a larger amount of the land (30,100 ha-71.8%) can be classified as more suitable for drip irrigation than surface irrigation.
Albaji et al. (2010b) investigated different irrigation methods based upon a parametric evaluation system in an area of 29,300 ha in the Abbas plain located in the Elam province, in the West of Iran. The results demonstrated that by applying sprinkler irrigation instead of surface and drip irrigation methods, the arability of 21,250 ha (72.53%) in the Abbas plain will improve. Albaji et al. (2010c) also provided a land suitability evaluation for surface, sprinkle and drip irrigation systems in Dosalegh plain: Iran. The comparison of the different types of irrigation techniques revealed that the drip and sprinkler irrigations methods were more effective and efficient than that of surface irrigation for improved land productivity. However, the main limiting factor in using either surface or/and sprinkler irrigation methods in this area were soil texture, salinity and slope and the main limiting factor in using drip irrigation methods were the calcium carbonate content, soil texture and salinity.
Albaji and Hemadi (2001) evaluated the land suitability for different irrigation systems based on the parametric evaluation approach on the Dasht Bozorg Planarian. The results showed that by applying sprinkle irrigation instead of drip and surface irrigation, the arability of 1611.6 ha (52.5%) on the Dasht Bozorg Plain will improve. In addition, by applying drip irrigation instead of sprinkle or surface irrigation, the land suitability of 802.4 ha (26.2%) on this plain will improve. Comparisons of the different types of irrigation systems revealed that sprinkle and drip irrigation were more effective and efficient than surface irrigation for improving land productivity. It is noteworthy, however, that the main limiting factor in using sprinkle and/or drip irrigation in this area is the soil calcium carbonate content and the main limiting factors in using surface irrigation are soil calcium carbonate content together with drainage.
The main objective of this research was to evaluate and compare land suitability for surface, sprinkle and drip irrigation methods based on the parametric evaluation systems for the Miheh Plain, Chahar Mahal and Bakhtyari province, in the center of Iran.
MATERIALS AND METHODS
The present study was conducted in an area of about 3011.9 ha in the Miheh plain, in the Chahar Mahal and Bakhtyari province, located in the center of Iran, during 2010-2011. The study area is located 60 km north-west of the city of Shahr e Kord, 32° 21’ 02” to 32°29’ 21” N and 50°14’ 43” to 50°24’ 13” E. The maximum and minimum elevation for the area is 3282 and 2179 m for the eastern and northwestern parts, respectively. Reviewing the existing statistics for a 18-year period (1978-2005) shows that the annual rainfall is 1409 mm, much of it rain in the autumn and winter (1205 mm). In this period, the average temperature is low and no plant is growing in the region in this time so no water is sued. Spring and summer when the plants are growing, there is little rainfall (204 mm) and the region is categorized as semiarid. The average annual temperature is 9.5°C. The annual evaporation of the area is 1865 mm. Most often the land are dry farmed and a limited area of lands are irrigated by fountains’ water or through pumping water from rivers. Currently, the irrigation systems used by farmlands in the region are furrow irrigation, basin irrigation and border irrigation schemes (Agricultural Jahad Organization and Chahar Mahal ve Bakhtyari, 2008).
The land evaluation was determined based upon topography and soil characteristics of the region. The topographic characteristics included slope and soil properties such as soil texture, depth, salinity, drainage and calcium carbonate content were taken into account. Soil properties such as cation exchange capacity (CEC), percentage of basic saturation (PBC), organic matter (OM) and pH were considered in terms of soil fertility. Sys et al. (1991) suggested that soil characteristics such as PBS and OM did not require any evaluation in arid regions, whereas clay CEC rate usually exceeds the plant requirement without further limitation, thus, fertility properties can be excluded from land evaluation if it is done for the purpose of irrigation.
To determine soil characteristics, it was used the semi-detailed soil survey report of the Miheh plain, Kohrang (Agricultural Jahad Organization and Chahar Mahal ve Bakhtyari, 2008). Based upon the profile description and laboratory analysis, the groups of soils that had similar properties and located in a same physiographic unit were categorized as soil series and were taxonomied to form a soil family as per the Keys to Soil Taxonomy. Ultimately, four soil series and 14 series phases were selected for the sprinkle, surface and drip irrigation land suitability.
In order to obtain the average soil texture, salinity and CaCO3 for the upper 150 cm of soil surface, the profile was subdivided into six equal sections and weighting factors of 2, 1.5, 1, 0.75, 0.50 and 0.25 were used for each section, respectively. The weight factors are used in order to give more importance to the upper part of profile where the root is developing more (Sys et al., 1991).
To evaluate the suitability of lands for surface, drip and sprinkler irrigation methods, the parametric evaluation system is applied. The system is based on morphology, physical and chemical properties of soil (Sys et al., 1991).
This method is consisted of six parameters including slope, drainage properties, electrical conductivity of soil solution, calcium carbonate status, depth soil and soil texture. Each of six above parameters is scaled according to the related tables and the capability index for irrigation (Ci) is calculated using them as the following formula:
where, A, B, C, D, E and F are soil texture rating, soil depth rating, calcium carbonate content rating, electrical conductivity rating, drainage rating and slope rating, respectively.
| Table 1: | Suitability classes for the irrigation Capability indices (Ci) classes |
| Fig. 1: | Soil map of the study area |
In Table 1, the ranges of capability index and the corresponding suitability classes are shown.
A semi-detailed soil map (Fig. 1) was used to develop land suitability maps for different irrigation methods (Fig. 2-5). All the data for soil characteristics were incorporated in the map using Arc GIS 9.2 software.
The digital soil map base preparation was the first step towards the presentation of a GIS module for land suitability maps for different irrigation systems. A total of 14 different Land Mapping Units (LMU) were determined in the base map. Soil characteristics were also given for each LMU. These values were used to generate the land suitability maps for surface, sprinkler and drip irrigation systems using Geographic Information Systems (GIS).
| Fig. 2: | Land suitability map for surface irrigation |
| Fig. 3: | Land suitability map for sprinkler irrigation |
| Fig. 4: | Land suitability map for drip irrigation |
| Fig. 5: | The most suitable map for different irrigation systems in the Miheh plain |
RESULTS AND DISCUSSION
The irrigation system applied in most lands of Miheh plain is surface irrigation. The major plants in agricultural lands and gardens are wheat, barley, walnut and peach (Agricultural Jahad Organization and Chahar Mahal ve Bakhtyari, 2008). The semi-detailed soil study resulted in recognition of 4 series of soil and altogether 14 series phases in the studied region. The series of soil are introduced in Fig. 1 as basis of evaluation. The soils of region are rated as Alfi soil, Molli soil and Incepti soil. The soil moisture regime is of Xeric and the soil temperature regime is Mesic. Non-agricultural lands consisting of residential area (0.87%) and (2.14%) hills constitute 90.9 ha (3.01%) of all 3011.9 ha area of region (Agricultural Jahad Organization and Chahar Mahal ve Bakhtyari, 2008).
As shown in Table 2 and 3 for surface irrigation, only the soil series coded 4.1 (73 ha-2.42%) was highly suitable (S1); soil series coded 1.1, 1.2, 1.3, 2.1, 2.2, 2.3 and 3.1 with the area of 1355.8 ha (45.01%) were classified as moderately suitable (S2).
| Table 2: | Ci values and suitability classes of surface, sprinkle and drip irrigation for each land units |
| *Limiting factors for surface irrigation,**Limiting factors for sprinkle and drip irrigation: s: Soil texture and/or calcium carbonate and t: Slope | |
| Table 3: | Distribution of surface, sprinkle and drip irrigation suitability |
| *Miscellaneous land: hill and residential areas | |
Soil series coded 2.4, 2.5, 2.6 and 3.2 with the area of 767.1 ha (25.47%) were found to be marginally suitable (S3). Soil series coded 1.4 and 1.5 with the area of 725.1 ha (24.07%) were classified as currently not-suitable (N1).
As shown in Fig. 2, analyzing the maps of land suitability for surface irrigation shows that a small area (located in the northwest) is highly suitable for surface irrigation. This was due to deep soil, good drainage, suitable texture, salinity and proper slope of the area, whoever the calcium carbonate content was high (27.54%). Most lands of the region are moderately suitable. In general, the soil texture of these lands is clay and silty clay loam and gently slope. Other factors such as salinity, soil depth and drainage have no effect on the land suitability of region. The map, also, shows that some of lands located in western and southeastern margins are of marginally suitable, because of gravels (15-35%), silty clay loam texture of the soil and improper slope (8-25%). The current non-suitable lands are located in northern and eastern parts of the region. They are current non-suitable lands because silty clay loam texture of the soil with coarse gravels (15-35%) and sharp slope (12-25%). The salinity, drainage and CaCO3 aren’t of limiting factors for surface irrigation in all lands of the region.
The land suitability of Miheh plain for drip and sprinkler irrigations was investigated (Table 2, 3). For sprinkler irrigation, soil series coded 1.3, 2.1 and 2.3 with the area of 907.6 ha (30.13%) were highly suitable (S1). Soil series coded 1.1, 1.2, 2.2, 2.4, 2.5, 2.6, 3.1, 3.2 and 4.1 with the area of 1288.3 ha (42.77%) were classified as moderately suitable (S2) while Soil series coded 1.4 and 1.5 with the area of 725.1 ha (24.07%) were marginally suitable (S3) for sprinkler irrigation.
The highly suitable for sprinkler irrigation (Fig. 3) were consisted of the southern and western parts and a small part of central area of Miheh plain; because of the soil depth, good drainage, soil texture, salinity and proper slope. Most parts of lands studied in Miheh plain are moderately suitable for sprinkler irrigation; because these lands are clay and silty clay loam texture and gently slope. A small part of the northwest lands is only moderately suitable for sprinkler irrigation; due to high percentage of CaCO3. Also, small parts in western, central and southeastern areas of this plain are moderately suitable; due to the sharp slope. The lands with marginally suitable are located in the northern and eastern parts of this plain; because of the soil texture of silty clay loam with coarse gravels (15-35%) and sharp slope (12-25%). The drainage, salinity and soil depth are not of the limiting factors for sprinkler irrigation in all studied regions.
The results from evaluating the suitability of lands for drip irrigation system based on parametric method showed that the soil series coded 1.1, 1.2, 1.3, 2.1, 2.2, 2.3 and 3.1 (1355.8 ha-45.01%) were highly suitable (S1). The soil series coded 2.4, 2.5, 2.6, 3.2 and 4.1 (840.1 ha- 27.89%) were moderately suitable (S2) while soil series coded 1.4 and 1.5 (725.1 ha-24.07%) were classified as marginally suitable (S3).
Figure 4 reveals the suitability of region for drip irrigation, most of studied lands (located in the southern and central parts and a small part in the northern lands of the studied region) are highly suitable for drip irrigation. In these lands, all of factors such as soil texture, salinity, calcium carbonate content, soil depth and slope are in the desired condition. The moderately suitable lands cover the central parts and some small parts in the northwestern and southeastern lands; because of silty clay loam soil with the coarse gravel (15-35%) and the medium calcium carbonate content (15.65% - soil series 2.4, 2.5 and 3.2). The lands in some parts of central, southeastern and southwestern areas are moderately suitable for drip irrigation due to the sharp slope. Also, because of high percentage of calcium carbonate content, a small part of northwestern area is classified as moderately suitable.
| Table 4: | The most suitable land units for surface, sprinkle and drip irrigation systems by notation to Capability index (Ci) for different irrigation systems |
The lands with marginally suitability are located in the northern and eastern areas of the plain. The limiting factors in these areas are the soil texture (silty clay loam with coarse gravel 15-35%) and the sharp slope. The soil depth, salinity and drainage are not of the limiting factors for drip irrigation in the studied region.
The mean capability index (Ci) for surface irrigation, sprinkler irrigation and drip irrigation are 62.56 (moderately suitable) 73.02 (moderately suitable) and 76.56 (moderately suitable), respectively. Comparing the capability index (Ci) for irrigation systems (Table 2, 4), it was revealed that the drip irrigation is more suitable than the surface and sprinkler irrigations in all series of studied lands (except the soil series 4.1). In the soil series 4.1, the surface irrigation is more suitable than the drip and sprinkler irrigations. It is because of the percentage of calcium carbonate content (27.54%) in these lands. Figure 5 shows the application of the most suitable irrigation system in the lands of Miheh plain. As shown in the map, the major part of Miheh plain is suitable for drip irrigation and a small part of the plain is suitable for surface irrigation.
Table 2 and 4 show that the suitability of 2848 ha (94.56%) lands of Miheh plain can be improved by using drip irrigation in place of surface and sprinkler irrigations. The surface irrigation has shown more suitability in 73 ha (2.42%) compared to drip and sprinkler irrigations. Comparison of different irrigation methods in the studied region showed that drip irrigation method is more efficient than surface and sprinkler irrigations (except for soil series 4.1) and it enhances the land suitability for irrigation goals. The second suitable option in the lands of this plain (except for soil series 4.1) is sprinkler irrigation enhancing the land suitability, compared to surface irrigation. The above discussion suggests that the irrigation systems suitable for Miheh plain are in order: drip>sprinkler>surface irrigation. In the studied region, the most limiting factors for surface irrigation are slope and soil texture and for sprinkler and drip irrigations are soil texture, slope and calcium carbonate content.
CONCLUSIONS
Considering the properties of different series of soil and other land properties, analysis and comparison of three irrigation systems was conducted. The results showed that drip and sprinkler irrigation methods are more suitable in many series of studied soil, compared to surface irrigation method. Because of shortage of the surface and ground water resources in semiarid regions, it is recommended to apply the under-pressure irrigation (drip and sprinkler) methods, instead of surface irrigation, in the studied region, in order to sustainable use water and soil resources.
Drip and sprinkler irrigation systems are more suitable than the surface irrigation in the whole region (except for soil series 4.1). The most limiting factors for drip and sprinkler irrigation methods are soil texture, slope and calcium carbonates content; whereas slope and soil texture are limiting factor for surface irrigation method.
In arid and semiarid regions, because of shortage of water, it is necessary to improve the water use efficiency in order to increase the agricultural production yield. Comparing the maps showed that drip and sprinkler irrigation methods can be considered as an optimal and useful solution in different policies for water management. Shifting from surface to drip and sprinkler irrigation method is resulting in saving water resources considerably. In general, drip and sprinkler irrigation methods preserve the soil at the field capacity using little amount of water, compared to the surface irrigation method. It would be useful to use under-pressure (drip and sprinkler) irrigation methods in Miheh plain.
ACKNOWLEDGMENT
The writers gratefully acknowledge the Research and Standards Office for Irrigation and Drainage Networks of Khuzestan Water and Power Authority (KWPA), Agricultural Jahad organization, Chahar Mahal and Bakhtyari and Shahid Chamran University for their financial support and assistance during the study and field visits.