Suitability Of Groundwater For Irrigation Purposes Research Articles

Assessment of groundwater suitability for irrigation purposes in the Fritissa region, Moulouya, Morocco

Under arid and semi-arid climate conditions, as is the case in many Moroccan regions, the availability and quality of water are the main keys to the sustainable development of agricultural zones. In the Fritissa region covering Middle Moulouya and a part of Lower Moulouya, North-eastern Morocco, irrigation practices are necessary for agricultural activities, in an environment with significant population growth, and limited water resources. The main aim of this study is to assess the quality of groundwater and its suitability for irrigation purposes, and to determine the possible water-rock interaction processes that influence the groundwater chemistry. The approach is based on the analysis of major ions contents and the calculation of quality indices namely pH, Electrical conductivity (EC), Total Dissolved Solids (TDS), Total Hardness (TH), Sodium Percentage (Na%), Residual Sodium Carbonate (RSC), Sodium Adsorption Ratio (SAR) and Permeability Index (PI) for 94 groundwater samples. Piper classification is used to determine the chemical water facies, while commonly used distribution and geochemical diagrams helped to discuss the possible interaction processes between water and aquifer rocks. The studied groundwater showed varying values for pH (5.8–8.8), salinity (367–3301 mg/L) and total hardness (15–186 mg/l as CaCO3). Ca-Mg-HCO3, Ca-Mg-SO4-Cl, and mixed water facies types are found, while one sample showed Na-K-SO4-Cl facies. The plotting of samples in Gibbs diagrams suggests possible water-rock interactions, that are confirmed by geochemical distribution diagrams. The Wilcox diagram showed that most of the water samples are of excellent to good and good to permissible categories, while the US salinity Hazard diagram revealed low sodium hazard and low, medium and high levels of salinity. Groundwater is suitable for irrigation according to current international standards if some precautions are considered.

Assessment of groundwater suitability for sustainable irrigation: A comprehensive study using indexical, statistical, and machine learning approaches

Groundwater quality for irrigation purposes varies across regions, countries, and specific locations, primarily due to factors such as groundwater extraction and utilization methods, the intensity of rainfall, and the subsequent recharge of aquifers. The present study aimed to evaluate seasonal groundwater suitability for irrigation purposes using indexical approaches, statistical computing, graphical plotting, and machine learning algorithms. Groundwater samples were collected from intensively cultivated areas before and after the monsoon season and were analysed for different physicochemical parameters. The results revealed that the cation concentration of groundwater during pre-monsoon season followed the order of Na+ (59.9 %) > Ca2+(21.9%) > Mg2+ (17.1 %) > K+ (1.2%), whereas, anion chemistry followed the order of Cl−(50.9%) > HCO3− (43.6%) > SO42− (4.0 %) > CO32− (1.4%). A significant increase in the concentrations of major cations (Ca2+ and Na+) and anions (Cl− and HCO3−) was observed during the post-monsoon season. Various irrigation suitability indices expressed that 98.9, 73.5, 99.5, 56.12, and 97.9 % of groundwater samples were found suitable for irrigation based on electrical conductivity (EC), residual sodium carbonate (RSC), sodium adsorption ratio (SAR), percentage sodium (Na%) and water quality index (WQI), respectively. The factor and cluster analyses revealed that salinity, natural processes, and anthropogenic factors are the key determining factors affecting the correlations among water quality parameters. In the purview of predicting groundwater quality, multiple linear regression (MLR) and artificial neural network (ANN) models excelled, with ANN consistently outperforming MLR. Thus, it can be concluded that seasonal shifts in groundwater quality for irrigation are influenced by monsoon dynamics, demonstrating notable changes in cation and anion chemistry, with ANN models displaying superior predictive capabilities of irrigation suitability.

Evaluation of shallow groundwater suitability for irrigation purposes: A case study from Doornfontein area, South Africa

Evaluation of shallow groundwater suitability for irrigation purposes: A case study from Doornfontein area, South Africa

Spatiotemporal Forecasting of the Groundwater Quality for Irrigation Purposes, Using Deep Learning Method: Long Short-Term Memory (LSTM)

Present study was conducted to predict the spatiotemporal groundwater suitability for irrigation purpose through deep learning method, Long-Short term memory (LSTM), in northwest of Iran. Sodium Adsorption Ratio (SAR) as a crucial irrigation water quality criterion for 101 sampling point for an 18-year data period from 2002 to 2019, was utilized as the input for deep learning model in order to forecast the irrigation water quality for the next year, 2020. To evaluate the model accuracy in spatiotemporal data forecasting, performance criteria such as Mean Absolute Percentage Error (MAPE), Root Mean Square Error (RMSE), and R were used which approved the model accuracy by 1.212, 0.312 and 0.89 of MAPE, RMSE and R, respectively. On the other hand, the model capability was assessed by RBIAS and generalization ability (GA), which results showed that LSTM model underestimated the targets with RBIAS equals to about 1.539, while had an acceptable GA, equals to 1.1832. Considering the carried-out map of irrigation water quality for the study area it was revealed that about 78% have the desirable to acceptable quality for irrigation and the about 22% are moderate to non-acceptable. The most non-acceptable points are juxtaposed to the residential area which shows the anthropogenic effect on groundwater quality through the fertilizers and the other pollutants, infiltered into the groundwater resources.

Impact of land use/land cover on groundwater resources in tropical unconfined aquifers of south-western India

Groundwater quality assessment is essential to understand land use impacts and implement water management plans. The present study aims to assess the impact of land use/land cover (LULC) on the groundwater table, and its quality in the tropical unconfined aquifers. Two hundred groundwater samples were collected from 100 sampling wells during monsoon and post-monsoon seasons. The drinking water quality index and irrigation quality indices were estimated based on the various parameters obtained from the laboratory analysis. Human health risk concerning nitrate contamination was evaluated based on the USEPA method. The land-use/land-cover map prepared using ArcGIS showed that the study area consists dominantly of croplands. Drinking water quality index results suggested that the groundwater samples were excellent to moderately suitable for drinking purposes. Only one sample was unsuitable for drinking. The different irrigation quality indices revealed various degrees of groundwater suitability for irrigation purposes. The spatial distribution of the corrosivity ratio suggests avoiding the metal pipe, for transportation of groundwater supply in the northern part of the study area. Fertilizers used in agriculture and soak pit leakages have contributed to high nitrate concentration in a few parts of the study area. Human health risk assessment showed that infants are vulnerable to non-carcinogenic health risks. The impact of the LULC assessment revealed that groundwater quality was moderately suitable for drinking in urban land. The study suggests implementing proper sewage treatment measures to avoid groundwater contamination. Overall, the findings are important in adopting site-specific, groundwater management strategies in the study area. Polluted and unpolluted areas demarcated in the study are beneficial for decision-makers to develop suitable groundwater management plans. The study recommends informed LULC development in the study area to improve groundwater quality and reduce human health risks.

AHP and GIS for assessment of groundwater suitability for irrigation purpose in coastal-arid zone: Gabes region, southeastern Tunisia.

In southern Tunisia especially in Gabes region, irrigated agriculture is the major economic sector. The intensive exploitation of groundwater have been gradually rising, leading the water quality to deteriorate. To ensure sustainable development and preserve water, soil, and land cover resources, a careful estimation of the irrigation water quality, which influence on the regional agriculture activities. The objective of this study is to investigate the irrigation water suitability based on hydrogeological, hydrochemical, and analytic hierarchy approach (AHP) and water quality index (WQI). Results highlighted that TDS of the groundwater ranged from 0.4 to 6 g/L. The most abundant chemical species in the water were Ca2+, Cl-, SO42-, and Na+, with mean concentration of 460 mg/L, 1320 mg/L, 1450 mg/L, and 1200 mg/L, respectively. The largest amounts were discovered along the shoreline and in deep aquifers embedded in Cretaceous sediments. AHP has used as multicriteria decision analysis, to weighting groundwater quality criteria, and groundwater suitability for irrigation has been mapped. Based on the Quality index "WQI", the water samples are categorized into three types: excellent, acceptable, and worthless. A 45% of sampled water is not suitable for irrigation use. However, groundwater quality is increasingly poor towards the coastal areas and north of the study area. This study concluded that the method adopted in assessing the groundwater quality in arid coastal areas led to important results and could be helpful scholar to improve their research especially in similar areas. It can also assist decision makers in taking proactive solutions to protect and preserve groundwater resources from pollution risks.

An integrated assessment approach for fossil groundwater quality and crop water requirements in the El-Kharga Oasis, Western Desert, Egypt

Study regionThe El-Kharga Oasis in the Western Desert of Egypt is selected as the study area due to its hyberarid climate condition and water scarcity. In this region, the fossil groundwater is the main water source; therefore, preserving groundwater quality and quantity is mandatory. Study focusThis study evaluated groundwater suitability for irrigation purposes and assessed the water requirements of cultivated crops to optimize the water supply in hyperarid climate regions. In total, 79 deep groundwater samples were hydrochemically tested to determine the suitability for irrigation by assessing the key water quality parameters. Spatial distribution maps of all chemical parameters, such as pH, EC, SAR, RSC, SSP, TDS, total hardness, Na+, K+, Ca++, Mg++, Fe, Mn, Cl-, and SO4—, were developed. The FAO CROPWAT 8.0 model, based on the Penman–Monteith equation, was used to forecast agricultural water requirements for three years, 2010, 2011, and 2012. New hydrological insights for the regionThe groundwater had medium salinity and low sodium in 84% of the cases. In comparison, high salinity was found in 16% of the samples, indicating that groundwater can be used for many soil types with a low risk of exchangeable sodium. Except for 15 of the 79 wells, all groundwater samples had chloride concentrations less than 100 mg/l. The sulfate ion distribution map showed a low sulfate ion content in the extreme western south. The total annual irrigation water requirements of all crops for 2010, 2011 and 2012 were 199.4, 215.1, and 231.7 million m3/year, respectively, reflecting a gradual increase of approximately 16.57 million m3/total area/year due to the expansion of the cultivated area. The analysis showed that modern irrigation systems reduced the amount of irrigation water by 32% and increased the cultivated area by 45% compared to conventional irrigation methods. Severe groundwater depletion occurred during the dry season from March to July, which exacerbated the water stress in the study region. The results confirmed that the region is under water stress. Accordingly, water conservation is urgently recommended.

Hydrogeochemical Characteristics of Groundwater in the Bassit Ophiolitic Area, Northwestern Syria

In order to evaluate the hydrogeochemical properties and the quality of groundwater in the Bassit ophiolitic area (Northwestern Syria), 27 groundwater samples were collected from springs and wells during dry and wet seasons. Physical-chemical parameters and heavy metal concentrations of groundwater samples were measured. The analytical results showed that the groundwater is very hard and slightly alkaline in nature. The concentrations of major ions are in the following order: Mg2+ > Ca2+ > Na+ > K+ and HCO32- > Cl- > SO42- > NO3-. The magnesium ion (Mg2+) has exceeded the permissible limit for drinking purpose, reflecting an influence of ophiolitic rocks on the local groundwater chemistry. The hydrogeochemical facies are mainly (Mg-HCO3) and (Mg/Ca-HCO3) types with a minor occurrence of Ca-HCO3 type. According to Gibbs diagrams, all samples fall in the rock dominance field and the chemical quality of groundwater is related to the lithology of the area. The maximum concentrations of some heavy metals in groundwater samples for two seasons are relatively low (16.9 μg/l Cr, 19.27 μg/l Ni, and 1.78 μg/l Co), which are under the permissible limit for a drinking purpose. Also to evaluate the groundwater suitability for irrigation purposes, Salinity hazard (EC), Sodium hazard (SAR, Na%) and magnesium hazard (MAR) were appraised. It is found that 89% of groundwater samples in two seasons were mainly classified as high salinity/low sodium, which suggests that this groundwater is unsuitable for irrigation. Only (11%) of samples were classified as medium salinity/low sodium and as such suitable for irrigation. The magnesium hazard showed that 82% of the samples had high values (MAR > 50%) and as such unsuitable for irrigation. Soil irrigated with such groundwater will not be exposed to any alkali hazard, but will suffer from salinity and magnesium hazard.

Evaluation on groundwater quality of limestone aquifer in Kinta Valley, Perak for the use as irrigation water

Groundwater has always been a secondary water source in Malaysia other than surface water. The recharge of groundwater had contaminated the aquifer after physical, chemical, biological, or radiological wastes from human activities are directly released into aquifer recharging sources, including river stream and lakes. The study covered limestone aquifers in Kinta Valley which were used as irrigation water in a few areas. Physicochemical data of groundwater sample and irrigation water quality indices (IWQI) including electrical conductivity (EC), sodium adsorption ratio (SAR), total dissolved solids (TDS), total hardness (TH), residual sodium bicarbonate (RSBC), soluble sodium percentage (SP), Kelly’s ratio (KR), magnesium adsorption ratio (MAR), and Doneen’s permeability index (PI) are used to evaluate groundwater suitability for irrigation purposes in Kinta Valley by the approaches of hydrochemistry. Based on the IWQI analysis on production well water, PA020 and PA113 are safe to use as daily irrigation water with stable water quality and no salinity hazard. Another two production wells, PA191 and PA302 are having fluctuation of increased sodium ions or bicarbonate ions in year 2018 and 2019 respectively but anyhow returned to a safe range in year 2020. More concerns should be taken to avoid mankind contamination to the limestone aquifer at PA191 and PA302.

Classification of groundwater suitability for irrigation purposes using a comprehensive approach based on the AHP and GIS techniques in North Kurdufan Province, Sudan

Deterioration of groundwater quality due to drastic human interventions is rising at an alarming rate particularly in lower- and middle-income countries. Yet, limited research effort has been devoted to monitoring and ascertaining groundwater quality. The present study develops a comprehensive irrigation water quality index (IWQI) for rating water quality of shallow and deep aquifers in North Kurdufan province, Sudan. The new approach is developed to overcome the deficiencies of the existing irrigation indices and coming up with a unified decision for classifying water quality for irrigation purposes. Because of these indices like permeability index (PI), sodium absorption ratio (SAR), etc., depending on specific elements, entirely subjective, as well as the great variations in their results, particularly when classifying water quality. Thus, IWQI is created based on eight indices that are generally used to evaluate irrigation water quality, plus three physicochemical parameters have been proven an impact on water quality. The analytic hierarchy process (AHP) is applied to minimize the subjectivity at assign parameter weights under multiple criteria decision analysis tools (MCDA). The spatial distribution of IWQI agrees with the spatial distribution of the most parameters. The results of our approach reveal that the majority of samples are suitable for irrigation uses for both aquifers except few wells in the confined aquifer. Also, noted that there are very variations in the irrigation indices results for classifying water quality. The comparison result showed that the new index robust, fair calculations and has best classifying of water quality.

GIS-based assessment of groundwater quality for drinking and irrigation purposes in central Iraq.

In many parts of the world, groundwater is considered to be a key source of fresh water for both the domestic and non-domestic sectors. Where groundwater extraction is implemented, systems to monitor water quality must ensure a safe and sustainable supply. Over the years, Iraq has suffered from surface water quality and supply problems, necessitating groundwater extraction in many regions. This study investigates groundwater quality in a region of central Iraq around Babylon city, covering an area of 5119km2. The data gathered for this study included maps, well locations and water quality data and was sourced from the relevant governmental departments. A base map of the focussed region was initially prepared following data collection. The analysed water quality parameters were used as an attribute database to produce thematic maps using a geographical information system (GIS) environment. In this paper, the water quality index (WQI) and the irrigation water quality index (IWQI) were calculated for different groundwater samples using various parameters including the Electrical Conductivity (EC), Cl-, HCO3-, Na+ and pH. Moreover, the groundwater suitability for irrigation purposes has been assessed using indices such as Kelly's ratio (KR), sodium absorption ratio (SAR), residual sodium carbonate (RSC), soluble sodium percentage (SSP) and permeability index (PI). Water quality index maps have been developed using the GIS environment. The obtained results reveal that the groundwater in the study location requires specific treatments to be usable.

Irrigation risk assessment of groundwater in a non-perennial river basin of South India: implication from irrigation water quality index (IWQI) and geographical information system (GIS) approaches

Groundwater is an important natural resource for irrigation purpose in the non-perennial River basin (Shanmuganadhi) of South India. The present investigation was conducted to determine the groundwater suitability for irrigation purpose, using irrigation water quality index (IWQI) with the application of GIS. A total of 61 groundwater samples collected from the present study region were chemically analyzed such as TDS, EC, pH, Ca2+, Mg2+, Na+, K+, HCO3−, Cl−, and SO42−. Groundwater quality shows slight alkalinity (7.11–7.95). The Wilcox, USSL, and Doneen’s diagrams, and RSC, KR, and MHR indices indicate that maximum groundwater sampling locations fall under the unsuitable category for irrigation purpose. According to the classification of IWQI, 57% of the total groundwater samples belongs to the poor to unsuitable water quality types for irrigation. The spatial distribution of IWQI displays that 77.27% of the present study region comes under the vulnerable zones such as moderate restriction (51.99%, high restriction (23.10%), and severe restriction (2.18%) water quality for irrigation purpose. Therefore, the present study suggests the suitable treatment methods for increasing the soil permeability and thereby to improve the crop production.

Hydrogeochemical modeling based approach for evaluation of groundwater suitability for irrigational use in Korba district, Chhattisgarh, Central India

Systematic assessment of groundwater suitability for irrigation purpose was evaluated in Korba district, Chhattisgarh, Central India. As a part of the assessment, groundwater physico-chemical data of 56 locations were considered. Ascertaining the groundwater suitability and its characteristics, various quality indices and hydrogeochemical studies were performed. Quality results showed that groundwater of the study area was mostly alkaline in nature, where a total of 17% groundwater samples were found hard to very hard, 9% were slight to moderate hazard, and 4% were high saline type. Chemical indices, namely Sodium percentage (Na%), Sodium adsorption ratio (SAR), Residual sodium carbonate (RSC), Permeability Index (PI), Kelly’s ratio (KR) and Magnesium adsorption ratio (MAR) were evaluated. According to the computed indices, majority of the samples were found to be suitable for irrigation. Based on USSL plot, around 54% of samples fell in C1-S1 and C2-S1 fields, indicating low to medium salinity with a low alkali hazard. Hence, groundwater fell under C1-S1 and C2-S1 fields can be used to irrigate all kind of soils with marginal increase of risk level for exchangeable Na+ content. Results of hydrogeochemical model suggested that groundwater of the study area were mainly influenced by rock-water interaction phenomena. Groundwater hydrogeochemical facies was characterized through Piper plot and Chadha’s diagram, which showed Ca–Mg–HCO3 type groundwater as the dominating facies within the study region.

Hydrogeochemistry and evaluation of groundwater suitability for irrigation purpose in the Mornag region, northeastern Tunisia

In semiarid regions, salinization and anthropogenic contaminants are considered as the principal threat to groundwater resource availability. Consequently, the origin and processes of salinization should be identified, to take a sustainable measurement to mitigate these problems. In the present study, groundwater samples from 18 dug wells were collected during the sampling campaign carried out in May 2016 in order to identify the main natural and anthropogenic processes that control the quality of groundwater in the Mornag shallow aquifer (northeastern Tunisia) and to evaluate its suitability for agricultural irrigation purpose. This may create a clear database for decision maker to take suitable actions to sustainably manage the groundwater resources. The hydrogeochemical parameters (major ions concentration, pH, TDS, EC) were examined to assess the quality of groundwater and to identify the main mineralization processes. Permeability index (PI), percentage of sodium (%Na) and the ratio of sodium adsorption (SAR) were investigated to evaluate the groundwater suitability for irrigation. It has been demonstrated that the major ions abundance follows the order of sodium > calcium > magnesium > potassium and chloride > sulfate > bicarbonate > nitrate. Dissolution of evaporite minerals, such as halite, gypsum and anhydrite, and reverse ion exchange are the predominant processes of groundwater mineralization, generating the Cl–SO4–Ca and Na–Cl major water types. The calculated irrigation water quality index displayed that 55% of the Mornag groundwater samples are distinguished by elevated SAR and PI, suggesting their unsuitability for irrigation. So, the present study has provided a precious insight into the major geochemical processes occurring in the Mornag shallow groundwater and their suitability for irrigation which will support future management of these resources.

Potential Use of Alluvial Groundwater for Irrigation in Arid Zones - Mhamid Oasis (S Morocco)

Abstract In arid zones, the availability of fresh water is usually very limited because of high salinity, which greatly limits their use for irrigation purposes. High mineralization of water used for irrigation leads to increased soil salinity. The aim of the study was to examine the potential use of alluvial groundwater for irrigation in arid zones. The works were conducted in the Middle Draa Valley in southern Morocco (the Mhamid Oasis) in October 2015. Water samples of alluvial groundwater were collected for laboratory analysis from 42 wells located in the oasis. In order to determine the possibility to use the water for irrigation purposes, the Sodium Adsorption Ratio (SAR), sodium percentage (%Na), permeability index (PI), Kelly’s ratio (KR), magnesium hazards (MH) and electrical conductivity (EC) were assessed. EC values, exceeding 3000 μS·cm-1 in all the samples, classify the water as unsuitable for irrigation. MH and the KR indexes show that 30% of water samples represent levels making them unsuitable for irrigation. SAR confirms the very high degree of susceptibility of the analyzed waters to salinity hazard. The PI index of these waters is moderate, however in terms of sodium content they can be deemed suitable for irrigation purposes. It has been found that even within a small area of the oasis, a very large differentiation in the alluvial groundwater suitability for irrigation purposes occurs.

Evaluation of Groundwater Suitability for Drinking and Irrigation Purposes in Toba Tek Singh District, Pakistan

Correlating the physicochemical parameters for assessment of the groundwater quality has emerged as a very useful approach for water use. Taking water samples from the Toba Tek Singh District of Pakistan, this study assess the water quality for drinking and irrigation purposes. A sum-total of 72nos. groundwater samples were collected and analyzed for the purpose of different water quality parameters including sodium (Na+), potassium (K+), calcium (Ca2+), magnesium (Mg2+), bicarbonate (HCO- 3), chloride (Cl-), sulphate (SO4 2-), pH, electrical conductivity (EC), total dissolved solids (TDS) and total hardness (TH). The results obtained were, then, compared with the standard desirable limits of physicochemical parameters prescribed by World Health Organization (WHO), Pakistan Standards and Quality Control Authority (PSQCA) and Pakistan Council of Research in Water Resources (PCRWR) for drinking purposes. In order to classify the groundwater suitability for irrigation purpose, parameters such as sodium adsorption ratio (SAR), percent sodium (PS), permeability index (PI), residual sodium bicarbonate (RSBC), Kelly’s ratio (KR), and magnesium adsorption ratio (MAR) were also calculated on the basis of chemical data. After that, the correlation coefficients between different physicochemical parameters were calculated to identify the highly correlated and interrelated parameters for water quality. Different plots like Piper, Durov, Schoeller and Stiff diagrams were drawn to classify the groundwater ability for different purposes. These several classifications show most of groundwater samples falling within the safe limits and thus suitable for drinking and irrigation purposes, except of a few samples with a caution that it may get worse in the future.

Prediction of groundwater suitability for irrigation using artificial neural network model: a case study of Nanded tehsil, Maharashtra, India

This study presents an artificial neural network (ANN) model predicting values of sodium adsorption ratio (SAR), residual sodium carbonate, magnesium adsorption ratio, Kellys ratio and percent sodium (%Na) in the groundwater of Nanded tehsil. The 50 groundwater samples were analyzed for different physicochemical parameters such as pH, EC, TDS, Ca, Mg, Na, K, Cl, CO3, HCO3, SO4 and NO3, for the pre monsoon season 2012. The ANN model is developed through R programming and compared with MS-Excel software. These parameters were used as input variables in the ANN based groundwater quality indices for irrigation suitability prediction. The best back propagation algorithm and neuron numbers were determined for optimization of the model architecture. The resilient backpropagation algorithm with weight back tracking was used for optimization of seven neurons through sensitive analysis. It showed that a network with seven neurons was highly accurate in predicting the irrigation suitability indices. The relative mean squared error, coefficient of determination (R2) and mean absolute relative error between experimental data and model outputs were calculated. It is observed that is a good agreement between actual data and ANN outputs of groundwater for irrigation suitability indices for training and testing datasets. The spatial distribution maps of measured and predicted values of irrigation indices were prepared using ArcGIS software. Hence, the result confirms that the ANN model is an applied tool to predict the groundwater suitability for irrigation purpose in Nanded tehsil.

A Gis-Based Assessment of Groundwater Suitability for Irrigation Purposes in Flat Areas of the Wet Pampa Plain, Argentina

The Pampa in Argentina is a large plain with a quite obvious dependence on agriculture, water availability and its quality. It is a sensitive environment due to weather changes and slope variations. Supplementary irrigation is a useful practice for compensating the production in the zone. However, potential negative impacts of this type of irrigation in salinization and sodification of soils are evident. Most conventional methodologies for assessing water irrigation quality have difficulties in their application in the region because they do not adjust to the defined assumptions for them. Consequently, a new GIS-based methodology integrating multiparametric data was proposed for evaluating and delineating groundwater suitability zones for irrigation purposes in flat areas. Hydrogeological surveys including water level measurements, groundwater samples for chemical analysis and electrical conductivity (EC) measurements were performed. The combination of EC, sodium adsorption ratio, residual sodium carbonate, slopes and hydraulic gradient parameters generated an irrigation water index (IWI). With the integration of the IWI 1 to 3 classes (categories of suitable waters for irrigation) and the aquifer thickness the restricted irrigation water index (RIWI) was obtained. The IWI's index application showed that 61.3 % of the area has "Very high" to "Moderate" potential for irrigation, while the 31.4 % of it has unsuitable waters. Approximately, 46 % of the tested area has high suitability for irrigation and moderate groundwater availability. This proposed methodology has advantages over traditional methods because it allows for better discrimination in homogeneous areas.

Groundwater Suitability for Irrigation: a Case Study from Debre Kidane Watershed, Eastern Tigray, Ethiopia

The present paper tries to assess groundwater suitability for irrigation purpose in Debre Kidane Watershed (45.09 km2), northern Ethiopia. The goal was to evaluate the suitability of the groundwater for irrigation, examine the water types and to investigate possible long and short term impact on groundwater quality. Thirty six water samples each were collected in rainy and dry (irrigation) seasons from the active shallow hand dug wells. The well selection for detailed study and water sampling was done using stratified followed by random sampling technique. The number of wells selected for study is accounting 10% of the total available hand dug wells in the area. Parameters such as electrical conductivity (EC), pH, Total Dissolved Solids (TDS), temperature and other physical properties were recorded in the field. Major anions and cations (Ca2+, Mg2+, K+, Na+, CO32-, HCO3-, Cl-, SO42- and NO3-) were analyzed in the laboratory. Chemical data suggests that the water type in the area though varies from Mg-HCO3, Ca-HCO3, Mg-Cl, Na-HCO3 to K- HCO3, predominantly it is mixed cation-HCO3 type in the rainy season; and Ca-HCO3 (Piper diagram) and Na-HCO3 (Stiff diagram) in irrigation season. Dominance of Na in irrigation season and increase in Sodium Absorption Ratio (SAR) are primarily due to possible increase of Na absorption in the soil replacing Ca. According to the guidelines for irrigation water quality, the groundwater is suitable for irrigation with some minor exceptions. In rainy season, 89% of the samples fall under the water class “good” and 11% “permissible” whereas in irrigation season only 30% are classified as “good” and 70% under “permissible” class. Toxicity in terms of SAR and salinity though presently under control and there is no specific toxicity effect on vegetables and field crops, however, there are indications of their increase in due course of time if proper measures are not taken. Keywords: Groundwater, Irrigation, Salinity, SAR, Toxicity, Water quality, Hand dug well, Ethiopia.