Suitability of Shallow Aquifer Groundwater in Vojvodina for Irrigation

Research article

Sanja Mrazovac Kurilić1, Violeta Cibulić1, Vladanka Presburger Ulniković1, Novica Staletović1, Lidija Stamenković2

 

1 University “Union-Nikola Tesla”, Cara Dušana 62-64, Belgrade, Serbia; E-mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it
2 College of Applied Studies, Filipa Filipovića 20, Vranje, Serbia

 

Abstract

This paper presents the results of testing the quality of groundwater from shallow aquifer in Vojvodina province (northern Serbia) for irrigation purposes. The groundwater samples were collected at 22 sites. The quality indicators which were the basis for assessing the possibility of irrigation water application are as follows: concentration of sodium ions, sodium absorption coefficient, RSC, magnesium hazard and permeability index. Based on the spatial distribution of the presented indicator values, the state of groundwater quality of the shallow aquifer in Vojvodina for irrigation purposes is assessed as satisfactory. The knowledge generated from this study can contribute to appropriate irrigation water use and agricultural policy for sustainable smallholder irrigation development in the region.

Keywords: groundwater, irrigation, water quality, Vojvodina province.

Introduction

 

The majority of the northern part of the Republic of Serbia, Vojvodina province, is part of the southeastern part of the Great Pannonian Basin (Figure 1). The Pannonian Basin is an area rich in groundwater (Polomčić i dr. 2011). In Vojvodina groundwater is the predominant source of drinking water for settlements, but is also used for irrigation purposes, which is very important because it is a highly agrarian area.

The quality of groundwater primarily depends on the physical and chemical characteristics of the soil and rocks surrounding the observed spot (Matthess 1982). Water-soil interaction is a continuous process that takes place over a various periods of time, depending on different factors. The chemical composition of groundwater is a crucial factor determining its suitability for use for human consumption, industrial purposes or in agriculture (irrigation).

The groundwater of the analyzed area is widely used for irrigation. In Vojvodina region groundwater used for land irrigation is abstracted from a shallow aquifer, which is located at a depths of up to 20 m. Irrigated agriculture is dependent on an adequate supply of water of appropriate quality. The suitability of water for irrigation is determined by laboratory analysis of water samples, using the following water quality parameters: pH; salinity, content of sodium, carbonate and bicarbonate, trace elements, toxic anions, nutrients, chlorides. Laboratory results of all the above parameters gives a clear picture of the quality of water and its suitability for irrigation of agricultural land.

The suitability of groundwater for irrigation purposes depends on its chemical composition, namely, mineral salts. Salts can contain certain smaller amounts of substances that originate from the dissolution of the surrounding soil and the rocks in which the groundwater is located.

Important chemical indicators for determining the validity of irrigation water are the sodium content or the danger of alkalis which is expressed through electroconductivity, sodium adsorption coefficient (SAR), sodium content in %, and residual sodium carbonate (RSC) (Robbinson, 1984; Pfeifer et al., 1999; Van de Graaff & Patterson, 2001; Prasad et al., 2001; Bauder et al., 2007; Seilsepour et al., 2009; Gungor & Arslan, 2016; Manimaran 2016).

Figure 1 provides an overview of the study area with 22 marked sites where testing of groundwater from shallow aquifer was performed.

 

Materials and Methods

The criteria for assessing the quality of irrigation water are partially defined by the Decree on the Limit Values of Pollutants in Surface Water and Groundwater and Sediment (“Official Gazette of RS” No. 50/2012), as well as by the Ordinance on permitted quantities of hazardous and harmful substances in soil and irrigation water and methods of their testing (“Official Gazette of RS” 1994).

Electroconductivity (EC) is a measure of the degree of mineralization of water that depends on the interaction of water and rock (Eaton, 1950). The EC of water for irrigation becomes one of the important parameters for estimating the total chemical validity of groundwater and is used to compare water in different areas. (Freeze and Cheery, 1979).

EC and Na+ concentrations are very important data for irrigation water classification. High salt content in irrigation water causes osmotic pressure in soil solution. In addition, salts directly influence the growth of plants, the structure and permeability of the soil, the aeration, the texture, and make the soil heavy.

In the procedure of assessing the suitability of water for use for irrigation, a number of classifications are available whose limits are not adapted to the conditions prevailing in Serbia. The regulations that are applied in Serbia do not prescribe, nor recommend the specific method and dynamics of the usability assessment to water users. Therefore, several procedures and classifications are in used in practice, often performed in parallel and compared, but it can be advised to to perform additional assessment using the methodology in this paper.

The assessment of water quality for irrigation is a necessary step in irrigation planning and operation, in order to prevent adverse impacts on natural resources such as land and groundwater, as well as plants and equipment used. In Serbia, the Law on Agricultural Land, the Law on Water and the Law on Environmental Protection provide the regulatory framework for monitoring of the usability of water for irrigation. However, regulations do not define the way in which it should be done, nor a classification according to which the water for irrigation will be classified. For this purpose, it is customary to use FAO classifications and classifications of the US laboratories for saline soil (USSL). A Neigebauer classification, which has been developed for areas in Vojvodina, is also used. It is common practice that the listed classifications provide different assessment of suitability of water for irrigation, therefore it is sometimes necessary to introduce a "supplementary" assessment/classification to eliminate differences that may exist between different classifications and to reach appropriate conclusions. This "supplementary" assessment implies the content or relations of cations and anions and the mineralization components of water: the values of residual sodium carbonate, the ratio of hydrocarbons and calcium, the relative magnesium content, the relative sodium content, and the index of permeability. Good water quality for irrigation according to the "supplementary" classification implies acceptable ranges of the stated values of parameters and their relationships.

USSL (United States Salinity Laboratory) from the US Department of Agriculture has adopted several techniques that are used to test water quality for agriculture. Based on the knowledge of certain chemical parameters values, an assessment of the irrigation water quality is performed.

Na% (1) is a way of assessing the quality of water for irrigation based on the concentration of sodium ions in water.

 

Figure 1. A) Map of Europe and Serbia; B) Map of the area with marked sites that were analyzed.

 

Na%=(Na+ + K+)*100/(Ca2+ + Mg2+ + Na+ + K+)      (1)

SAR (2) is the sodium adsorption coefficient in the soil and is used to estimate the harmfulness of sodium levels retained in the soil. Excessive sodium levels in water for irrigation of soil leads to undesirable effects such as change in soil properties, reduction of its permeability and changes in soil structure (Kelly, 1957).

SAR=Na+ / sqrt ((Ca2+ Mg2+)/2)      (2)

Bicarbonate and carbonate ions combined with calcium or magnesium will precipitate as calcium carbonate (CaCO3) or magnesium carbonate (MgCO3) when the soil solution concentrates in drying conditions. The concentration of Ca and Mg decreases relative to sodium and the SAR index will be bigger. This will cause an alkalizing effect and increase the pH. Therefore, when a water analysis indicates a high pH level, it may be a sign of a high content of carbonate and bicarbonates ions.

Residual sodium carbonate RSC (3) was often used in assessing the quality of water for irrigation. Harmful effects of carbonates and hydrocarbonates on the quality of groundwater is determined by calculating the RSC coefficient. (Eaton,1950).

RSC = (CO3+HCO3)-(Ca2++Mg2+)      (3)

A higher amount of magnesium in water affects the quality of the soil by alkalizing it and thus reducing crop yields. Szabolcs and Darab (1964) have defined the concept of magnesium hazard MH (4) for water used for soil irrigation.

MH = Mg2+x 100/( Ca2++Mg2+) (4)

According to Doneen-u (1964), the criteria for assessing the quality of irrigation water based on the soil permeability index PI given in (5). The soil permeability is under the influence of long-term water use for irrigation and Na, Ca, Mg and HCO3 content in soil.

PI=(Na+ + sqrt (HCO3-))*100 / (Ca2+ + Mg2+ + Na+)      (5)

Irrigation water quality indicators are calculated using the content of ions expressed in mEq/l. All calculations were done in the Excel program package, while the results were graphically displayed using the software package Surfer 12.

 

Results and Discussion

Table 1. Statistical analysis of measured parameters.

 

Based on the results of regular monitoring (Table 1) of main ions concentrations for the shallow aquifer at 22 sites for 2016, the basic indicators of irrigation water quality are calculated: Na%, SAR, RSC, MH and PI. Based on the calculated values of the indicators, Figures 2-7 show the spatial distribution of the values of each individual water quality indicator.

 

Figure 2. Map of the area with spatial distribution of MH indicator values.

 

Figure 3. Map of the area with spatial distribution of Na% indicator values.

 

Figure 4. Map of the area with spatial distribution of PI indicator values.

 

Figure 5. Map of the area with spatial distribution of RSC indicator values.

 

Figure 6. Map of the area with spatial distribution of SAR indicator values.

 

After the analysis, it can be noted that in most of the observed territory, the quality of water by a particular parameter is satisfactory, while the increased values can be noticed at sites 13 and 15 for MH, 20 for Na%, 20 and 15 for PI, 20, 14 and 15 for RSC, and 20 for SAR. It can be noted that a total of 12 sites out of 22 originating from the shallow aquifer possess excellent water quality for irrigation. A total of 9 out of 22 sites exhibit average quality of water for irrigation, while site number 20 - Sečanj, in Banat, was the only site deemed to have groundwater of unsuitable characteristics. In percentage terms, 96% of groundwater from shallow aquifer from total 22 sites can be safely used for irrigation purposes.

Based on the presented data, it can be concluded that the shallow aquifer in Vojvodina mainly contain water of acceptable quality for irrigation.

 

Conclusion

The classification of water quality of the shallow aquifer in Vojvodina province for purposes of soil irrigation was carried out in this paper. The analysis was based on regular monitoring of data at 22 groundwater monitoring stations. The measured water quality parameters included ions of sodium, magnesium, potassium, calcium, hydrocarbonate, chlorides and sulphates.

Based on the measured values, water quality indicators for irrigation were determined: Na%, SAR, RSC, MH and PI, and based on the values of these parameters, the spatial distribution of the values of each individual site is given. It can be concluded that only groundwater from the site No 20 can be characterized as unsuitable for irrigation.

Based on the measured values indicators of water quality for irrigation: Na%, SAR, RSC, MH and PI, were determined, and based on the value of these parameters, the assessment of groundwater suitability for irrigation at each site was given. It can be concluded that 41% of the analyzed sites show good water (shallow aquifer) quality for irrigation, 55% are of excellent quality, while only one site (Sečanj) or 4% of the total number of sites have poor water quality for irrigation.


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