CHAPTER II
AREA, TOPOGRAPHY AND CLIMATE CHAPTER II
AREA, TOPOGRAPHY AND CLIMATE
2.1 Area - Location » Boundrles
The area comprises of two districts of Konkan i.e. Thana and Raigad; the hilly terrain of Ahmednagar, Pune and Satara districts. It is located between 17° 50*- 19® 50* North latitudes and 73° - 75° 50* East longitude. It is bounded by Arabian sea towards west along its entire length while eastern boundry comprises of crest of Ghats and the gentle spurs extending towards east. Towards north are / Nasik district and semiarid parts of Gujarat. Towards are southj^ Kolhapur, Sindhudurga districts and evergreen forests of Goa and Karnataka (Map 2.1).
2.2 Physiography
The area is varied physiographically. Western ghats which are formed of continuous chain of hills parallel to sea coast dominate the topography of the region. The average height of ghats is 1300 m above mean sea level. From the hill range lateral spurs of low hills run towards east and west. The Konkan region forms a coastal strip of about 25 - 40 km between base of the ghat? and the sea. There is an abrupt fall in elevation towards Konkan expos ing a vertical profile as seen at Arthur seat, Mahabaleshwar, Map 2.1 B
Varandha ghat and Harishchandragad. Towards east the hilly slope merges into Deccan plateau with average altitude of 400*600 m above mean sea level. The Konkan plains and Deccan plateau are linked with few gaps i.e. ghats. The crest of ghats carry at their top, plateaus, the tablelands e.g. Mahabaleshwar (143^ m), Harishchandragad (14^4 m} etc. The highest peak is at Kalsubai (I646 m).
According to climatological and physiographical condi tions area can be divided into five zones - (1 ) The coastal region and alluvial plains; (2) Low lying hills; (3) Crest of Ghats; (4) Eastern gentle spurs, and (5) Eastern plains.
2.3 Geology (Map 2.2)
Geologically a major part of this area consists of an extensive Deccan Trap Formation consisting of lava flows of basaltic composition, which provides the parental material for local soils. The trap is usually capped with laterite at higher elevations. The mountain tops are usually flat and very steep towards west, while the eastern slopes are gentle and descend down gradually into the lower plains. The basaltic trap capped with laterite, giving rise to red loamy, porous and acidic soils.
2.4 Soil (Map 2.3)
Soil from this area can be classified into two types > Map 2.2
--I Deccan trap Map 2.3
Costal saline Latehte and lateritic soils
Yellowish brown soils Medium black soils
Coarse shallow soils 1) Soil developed hy natural degradation of underlying rocks, and 2) Soli transported from elsewhere and deposited in successive layers of varying depths. These can further be classified into black, red and grey according to their local elevation and composition. Black soils belong to the flat eastern plains and occurring in many layers of few meters each. This often gets mixed with sand and clay. Laterltic red soil is mixed with gravel. Grey soil is very loose, coarse, gravelly and is subjected to erosion.
2.5 Hydrography
The river system from the area under study falls into two groups due to peculier physical features of the area under consideration. 1 ) Long Deccan rivers and their tributaries, (2) Short and swift Konkan rivers (Map 2.4).
The main Deccan rivers are Godavari, Bhlma and Krishna which flow through the plateau east-ward^i' , They have high water during monsoon i.e. July to September and low water mark in April and May.
Godavari basin lies between Sahyadrles in the west and eastern limits of state and covers an area of 1 ,00,000 km within Maharashtra State. Varna, Pravara and Indravati are the left tributaries.
Bhlma is a big tributary of Krishna. It rises near Bhlmashankar in Pune District. The basin lies between Map 2.4
-Ahmadnagar-
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7A
Godavari basin
-^•^1 Bhima basin Krishna basin 10
Mahadeo range and Balaghat range. Mula, Mutha, Nira and Man are main right tributaries while Ghod and Sina are the left tributaries.
Krishna basin is formed along the sides of Krishna river which rises in the northern slope of Mahabaleshwar,
Konkan rivers are small and have a swift current. Raising in steep western scarp of the ghats at the height of about 1000 m and drain in to the Arabain sea. These have high waters in monsoon and are dry in suauner. Sea water enters into these rivers during high tide forming creeks.
The area has a network of water reservoirs construc ted through dams for hydroelectricity and irrigation faci lities. Major amongst them are Panshet, Khadakwasla, Bhatghar, Bhandardara^ Kukdi, Mula etc.
2.6 Climate (Graph 2.5)
Sahyadri plays significant role in determining climate of the area. In the narrow strip between Sahyadri and Arabian sea climate is typical coastal climate >^ile on the lee side of the ghats there is continental climate. This contrast is further sharpened by the fact that rain bearing monsoon winds derived from the sea are limited to the coastal lowlands by orographic barrier. The rain clouds penetrate w a
Uj
g -J o Q
Or
tr 3 r\) 11 into deeper areas from the ghats of Sahyadrl, The climate of the area under study is monsoonic.
2.7 Rainfall (Map 2.6)
The Western slopes of Sahyadri facing to Arabain Sea receive rainfall between 1500 - 2000 mm and it increases from coastal plains to summit of ghats where the rains are more than 4000 mm. There is a considerable decrease in the rainfall along eastern slopes. Within a distance of about a hundred kilometers from the crest of the Sahyadri the rainfall shows a sharp decline in parts of Ahmednagar, Pune and Satara districts.
The transition towards immediate eastern plains from Western ghats is marked by the rainshadow areas, where there is an abrupt decrease in the precipitation.
1) Rainshadow area between iOiandala - Kedgaon (Graph 2.7)
Name Distance Rainfall
Khandala (Pune dist) Crest of ghat 5000 mm 5 km east mm Lonavala I 4000 Talegaon 40 km east 1000 mm Pune 70 km east 600 mm Kedgaon 110 km east 300 mm Map 2.6
Above 200 100-200 80-100 l S 3 60-80 lLlI I ' 50-60 Below 50 GRAPH OF RAINSHADOW AREAS Graph 2.7 12
2) Rainshadow area between Mahabaleshwar - Nira (Graph 2.7)
Location Distance » '• Rainfall
Mahabaleshwar Crest of ghats 6635 mm (Satara dist.) Pachgani 19 km east 2500 mm Wai 35 km east 1000 mm Nira 95 km east 300 mm
The rapid change in rainfall influences the vegeta tion considerably which ranges from semievergreen to semi- arid or thorny type,
2.8 Temperature
There are three marked seasons viz., the wet season from mid-June to October, the cold season from November to February and hot season from March to mid-June. 1) In the coastal districts i.e. Konkan region temperature ranges from 17® C to 28® C in winter and from 19° C to 30® C in sxuraner. It is controlled by sea breezes. 2) Along the crest of ghats, climate is cooler even in middle of summer. In winter tempe rature ranges from 17® C to 21® C and in summer 18® C to 27® C. 3) Along the eastern plains temperature goes to extremes in winter and summer* 13
2.9 Relative Humidity
The relative humidity of the coastal plains and western slopes of western ghats Is always more than 60% upto throughout the year. The high relative humidity is due to presence of moisture in air because of the vicinity to sea. On the Crestline of the ghats, the relative humidity is the highest of the area In rainy season due to high raln> fall. On eastern slopes of western ghats and eastern plains, the humidity gradually decreases due to ralnshadow area and far away from sea minimum J»8.2 - 7h»5% between winter to rainy season.
Table 1 : Relative humidity of different regions
No. Region Season Relative humidity
1. Coastal plains (Konkan) Winter 64.4 Summer 74.3 Monsoon S4.4 2. Western slopes of western ghat Winter 66.4 Summer 74.3 Monsoon 84.4 3. Crestline of ghats Winter 52.6 Summer 60.2 Monsoon 93.1 4. Eastern slopes of western ghats Winter 48.1 Summer 52.0 Monsoon 74.5 5. Eastern plains Winter 39.5 Summur 33.1 Monsoon 65.2 u
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