Effect of Agricultural activities on Surface water quality of Kolthur and Sampambole Lakes of Medchal Malkajgiri district, Telangana India

INTRODUCTION

One essential natural resource for the existence of all ecosystems on Earth is water. Less than 1% of the water resources on Earth, however, are available to people as fresh water, either as groundwater or surface water [1-2]. Water quality problems are often attributed to loadings of nutrients, chemicals, and pathogens into an aquatic system from point source and non-point source activities [3]. Out-dated agricultural management practices are the main source of contamination in a catchment’s surface and ground water. These include conventional irrigation techniques, the overuse of fertilizers for high product yields, the application of pesticides and herbicides, and poorly managed animal agriculture enterprises [4]. Additional factors include untreated sewage pollution, rainfall-induced air deposits, fracking, and deforestation. However, the research presented in this paper focuses on the relationship between agricultural management practices and the decline in water quality. These activities may result in fluxes of nutrients, chemicals, pathogens, and sediment, as high losses of nitrogen and phosphorus are the main cause of nutrient problems [4].  

Chemical fertilizers such as Nitrogen Phosphorus Potassium (NPK), urea and manure are widely applied on agricultural farm lands to improve crop yield thereby compromising the quality of the water sources [5]. Phosphorus is an important nutrient for plant growth. In aquatic systems, a lack of phosphorus often limits aquatic plant growth. Excess phosphorus is usually considered to be a pollutant. The present study focuses on the effects of agriculture on two Lakes i.e., Kolthur Lake and Sampambole Lake of Medchal-Malkajgiri district of Telangana State.

Study Area

Kolthur Lake and Sampambole Lake both are found in the Medchal Malkajgiri district in Telangana, India. It falls under Shamirpet mandal. The water samples were collected from eight (K1 to K8) and six (S1 to S6) sample locations of Kolthur Lake and Sampambole Lake of Medchal Malkajgiri district during all the three seasons i.e., during the pre-monsoon (PRM), monsoon (MN) and post-monsoon (POM) and are shown in table 1a, 1b and fig 1. Both lakes are surrounded by the agricultural fields as shown in fig 2 and 3.

MATERIALS AND METHODOLOGY

The parameters assessed were pH, electrical conductivity (EC), total dissolved solids (TDS), total alkalinity (TA), total hardness (TH), carbonates (CO₃^–), bicarbonates (HCO₃^–), sodium (Na), potassium (K), calcium (Ca⁺²), magnesium (Mg⁺²), chloride (Cl^–), fluoride (F^–), sulphates (SO₄^-2), phosphates (PO₄^-3), dissolved oxygen (DO), biological oxygen demand (BOD) and chemical oxygen demand (COD). The determination of Dissolved Oxygen (DO) was done at the field using portable DO meter. Then they were taken to the laboratory and refrigerated at 4°C. The samples used for determination of Biological Oxygen Demand (BOD) were directly collected in BOD bottles by adding some drops of magnesium sulphate solution to fix dissolved oxygen. All other physico-chemical analysis was done using the APHA standard methods for the twenty parameters. The results were compared with the BIS (2012) standards.

RESULTS AND DISCUSSION

The results obtained for the both Lakes i.e., Kolthur Lake and Sampambole Lake during the PRM, MON and POM including the minimum, maximum and average values are shown in the table 2 and 3 respectively. The pH values ranged between 7.44 to 8.45 and 7.56 to 8.39 for Kolthur and Sampambole Lakes respectively. The EC values were between 811 to 1077 μS/cm for the Kolthur Lake and between 995 to 1133 μS/cm for the Sampambole Lake. The TDS were found to be in the range of 519 to 690 mg/L and 637 to 725 mg/L for Kolthur and Sampambole Lake respectively and found to be exceeding the acceptable limits of BIS standards in all the three seasons.  The Turbidity was found to be in the range of 8 to 76 NTU and 8 to 94 NTU for Kolthur and Sampambole Lake respectively. It is also found that the turbidity was also exceeding the acceptable limits of BIS standards in all the three seasons.  The Nitrates (NO₃^–) during the post monsoon season for all the samples except K1 and K2, K3 and K5 samples of the monsoon season were found to be exceeding the BIS acceptable standards. All the samples of pre-monsoon were within the acceptable limits for the Kolthur Lake. The values ranged between 25 to 73 mg/L. For the Sampambole Lake, all the samples of pre-monsoon were within the acceptable limits. Whereas for the S2, S3, S4 and S5 and all other samples of post-monsoon were found to be exceeding the acceptable limits of BIS acceptable limit. The values ranged between the 38 to 81mg/L. Blue baby syndrome, also known as methamoglobianemia, is a common illness in infants caused by high nitrate concentrations in drinking water. The fact that nitrate can be transformed into nitrosamines by bacteria in the digestive tract, which may cause cancer, is significant and adds to the concern about nitrate’s effects on humans. Recent investigations have found that these compounds have strong carcinogenic effects. Water eutrophication, a condition where there are higher levels of nitrogen and phosphorous compounds in the water, leads to the growth of more aquatic plants and algae as well as the deterioration of the water environment and quality. This is one of the most significant adverse effects of intensive fertilizer use.

The Potassium (K⁺) was exceeding the BIS limits during the post monsoon season of both Kolthur and Sampambole Lakes. The values ranged between the 3.1 to 17.6 mg/L for the Kolthur Lake and 3.1 to 26.2 mg/L for the Sampambole Lake respectively.

The Phosphates (PO₄^2-) were also found to be exceeding the BIS standard value for all the three seasons in both the Lakes and it was found to be between 1.1 to 8.9 mg/L for Kolthur Lake and 1.6 to 6.5 mg/L for the Sampambole Lake. Phosphorus is recognized as one of the major nutrients contributing to the increased eutrophication of Lakes and other natural waters [6].

The Dissolved oxygen was found to be within the acceptable limits for both the pre-monsoon and post-monsoon except for the monsoon. All the samples of monsoon were exceeding the acceptable limits and the values ranged between 1.5 to 6.5 mg/L for the Kolthur Lake. For the Sampambole Lake all the values were within the acceptable limits and the values ranged between 1.8 to 5.7 mg/L. The increase in value can be attributed to the addition of oxidisable organic matter from the effluents, biodegradation and decay of vegetation at higher temperature thereby taking oxygen from water [7-8]. For the Biological Oxygen demand parameter all the samples for all the seasons were exceeding the acceptable limits and the values ranged between 20 to 130 mg/L for the Kolthur Lake. For the Sampambole Lake all the values were exceeding the acceptable limits in all the seasons and the values ranged between 30 to 130 mg/L. The chemical oxygen demand values were between 70 to 360 mg/L for the Kolthur Lake and between 73 to 360 mg/L for the Sampambole Lake.

The parameters like turbidity, total dissolved solids, potassium, phosphates, dissolved oxygen and biological oxygen demand are found are exceeding the BIS standards in majority of the samples, which can be used to determine the water pollution due to agricultural activities

The carbonates values ranged between the 10 to 20 mg/L for both Kolthur and Sampambole Lakes respectively. The bicarbonates values were between 80 to 190 mg/L for the Kolthur Lake and between 106 to 194 mg/L for the Sampambole Lake. The total alkalinity values ranged between 90 to 190 mg/L and 110 to 194 mg/L for Kolthur and Sampambole Lakes respectively. The calcium values were between 38 to 59 mg/L for the Kolthur Lake and between 32 to 60 mg/L for the Sampambole Lake. The magnesium values ranged between 10 to 23 and 10 to 22 mg/L for Kolthur and Sampambole Lakes respectively. The TH values ranged from 144 to 199 mg/L in Kolthur Lake and 155 to 199 mg/L in Sampambole Lake. The Chloride values were between 160 to 230 mg/L for the Kolthur Lake and between 169 to 225 mg/L for the Sampambole Lake. The sodium values ranged between 84 to 164 mg/L and 122 to 171 mg/L for Kolthur and Sampambole Lakes respectively. The sulphates values were between 60 to 134 mg/L for the Kolthur Lake and between 85 to 151 mg/L for the Sampambole Lake. The fluorides values ranged between the 0.27 to 0.68 mg/L and 0.35 to 0.78 mg/L for Kolthur and Sampambole Lakes respectively. The pH, TA, TH, Na⁺, Ca²⁺, Mg²⁺, Cl^– and F^–, all the samples in all the three seasons were found to be within the accepted limits of the BIS standard values.

CONCLUSIONS

In the present study few samples showed that the values of Nitrates and Phosphates increased from pre-monsoon to post-monsoon. It indicates that through agricultural runoff of fertilizers into the Lakes is increasing their concentrations. Lake waters are being polluted by various physico-chemical parameters like turbidity, total dissolved solids, phosphates, dissolved oxygen, and biological oxygen demand which are reported to be over the acceptable levels of BIS 2012. Determining the amounts of phosphorus species in the environmental matrix is therefore required in order to supply crucial information for evaluating the condition of ecosystems, looking into biogeochemical processes, and keeping an eye on legal compliance.

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