ABSTRACT

The Krishna river originates from the Western Ghats at Mahabaleshwar in the State of Maharashtra and flows south for about 260 km. During its course in this state particularly in the Satara, Sangli and Kolhapur districts, the river is subjected to several diversions for irrigation purposes and large amounts of industrial and domestic waste are dumped everyday threatening the quality of the river water. The present study was carried out to assess the impact of these diversions and other human activities on the salt build up in the river water as indicated by pH, conductivity, sodium, potassium, calcium, sulphate, chloride, alkalinity and bicarbonate content of the river water collected at ten different spots at comparable distances throughout the course of the river flow in the State of Maharashtra. The study clearly indicated that there is an increase in the salt buildup at an alarming rate within a very short distance of about 260 km. Significance of the findings is discussed.

INTRODUCTION

River water accumulates naturally large varieties of dissolved matter as it passes through soils and rocks on its way to sea. This typically includes such ions as calcium, magnesium, /sodium, sulphate, chlorides and bicarbonates. These plus minor amounts of other dissolved constituents are commonly referred to as salinity. The irrigation projects and diversions on the river enhance the process of salt buildup in river water (4,9).This water when used in agriculture accelerates the salt accumulation process in the soil as a result of evapotranspiration, thereby polluting soils and making them unfit for the crop growth forever. Such problems have earlier been studied in India (6, 7) Canada (8), S. Australia (2) and USA (2).

The river Krishna in the State of Maharashtra is subjected to many diversions for irrigation purposes during its course of flow of about 260 km. Intensive agricultural practices particularly the sugarcane cultivation along the banks of the river have made this region as one of the most agriculturally advanced area in this country. However, the reprecussions of irrigation through river water associated with improper water management are becoming evident in the light of growing problem of salt accumulation in this region. Several hundred hectares of land has already become worthless due to salt accumulation in very recent past. Present study was carried out to assess the salt buildup in the Krishna river water to understand the magnitude of the problem.

SAMPLING AREA AND METHODS

Table 1 : Important features of the sampling sites along the Krishna river in the State of Maharashtra

Sr.No.	Place	Distance from source, km	Important features
1.	Dhom	20	A dam is constructed on the Krishna river. Agricultural practices along the banks, less of sugarcane.
2.	Mahuli	45	Situated at the confluence of the Krishna and the Venna river. Little agriculture nearby.
3.	Rahimatpur	60	Little irrigation facility and less agriculture, soil rich in gravel.
4.	Umbraj	80	Situated at the confluence of the Krishna and the Tarale river. Little agriculture of sorghum and sugarcane, soil with gravel.
5.	Karad	100	Situated at the confluence of the Krishna and Koyna. Extensive sugarcane, cultivation. Weir is constructed for irrigation. Sewage of the city is discharged.
6.	Takari	125	Weir is constructed. Extensive sugarcane cultivation. Effluents from sugar and alcohol industry are discharged.
7.	Bhilawadi	170	Extensive sugarcane cultivation. More than 250 ha land became worthless in last two years only, due to salt accumulation.
8.	Sangli	214	Extensive sugar cultivation. Pastes from the city, sugar, alcohol, cotton mills and other industries are discharged.
9.	Ghalwad	244	Extensive sugarcane cultivation. More tnan 450 ha of land has become worthless in last two years due to salt accumulation.
10.	Narsinhawadi	261	Intensive sugarcane cultivation. Popular piligrim centre. Lot of human activity along the banks, particularly performance of holy religious rites.

The sampling was done in September, 1980. Samples were collected in jerrycans and were analysed for chlorides, sulphates, bicarbonates and alkalinity as per ISI methods (3); sodium, potassium and calcium using Flamephotometer (ELIGO Model CL- 24) (1); conductivity at 25°C and pH in the field using Direct Reading Conductivity Meter (Systronics Type 303) and pH meter respectively. All the analyses were done within 24 hr of collection. 

RESULTS AND DISCUSSION

The results of the analyses of water samples are presented in Table 2.

Table 2 : Chemical analysis of water samples of Krishna river.

Sr.No.	Sampling sites	Distance from source, km	pH	Conductivity, uS at 25°C	Chlorides mg / 1	Bicarbonates mg / 1	Alkalinity mg / 1	Sodium mg / 1	Potassium mg / 1	Calcium mg / 1	Sulphate mg / 1
1.	Dhom	20	7.3	330	24.8	128.1	40.0	2.5	1.5	4.5	1.8
2.	Mahuli	45	7.4	320	32.7	134.2	40.0	7.5	0.5	2.0	2.6
3.	Rahimatpur	60	7.2	340	38.7	381.2	39.0	8.0	0.5	2.0	3.1
4.	Umbraj	80	7.4	270	30.7	274.5	31.0	5.0	0.5	2.5	3.2
5.	Karad	100	7.5	330	38.7	117.1	46.0	5.5	1.5	3.0	2.9
6.	Takari	125	7.5	330	36.7	91.5	83.0	6.5	0.5	8.5	4.3
7.	Bhilawadi	170	7.7	350	29.7	265.3	30.0	8.5	1.5	4.0	5.2
8.	Sangli	214	7.1	630	100.3	244.0	34.0	13.0	0.5	10.0	6.9
9.	Ghalwad	244	7.4	350	25.8	179.7	26.0	9.0	1.5	7.5	8.0
10.	Narsinhawadi	261	7.4	350	25.3	288.7	25.5	9.0	0.5	8.5	4.4

pH of the water was found to be alkaline at all spots. It was maximum at Bhilawadi (7.7) and lowest at Sangli (7.1). The latter could be due to the discharge of large amount of sewage from the Sangli city.