Morphometric analysis using remote Sensing and GIS techniques of Pingalgarh watershed VNMKV, Parbhani, India

Introduction

The dimensions of study area lies amongst 19.25080 N latitude and 76.79520E longitude in Parbhani district of Marathwada region of Maharashtra state. The area of Vasantrao Naik Marathwada Krishi Vidyapeeth, Parbhani is approximately about 3043 Ha. The catchment area falls under semi-arid tropics. The slope of the land area varies from 0.5 percent to 1.5 percent, major area is under agriculture. The average annual rainfall of the study area is estimated as 938.7 mm. About 94% of the total rainfall is received during the months from June to September. Pingalgarh watershed flows across VNMKV, Parbhani main campus and it is a part of Godavari-Purna basin. The prominent stream namely Pingalgarh watershed flows about 8 km as a main drain line across university area. The catchment area falls under assured rainfall zone of Marathwada region. The soils in the region are deep black, medium black, coarse and shallow. The predominant soil in the region is Vertisol (Black cotton soil). Under rainfed agriculture, major kharif crops of the region are sorghum, cotton, pigeon pea, green gram, black gram, pearl millet and soybean, whereas major rabi crops are rabi sorghum, safflower, chickpea and sunflower. In this study, DEM are used for the analysis of relief features in the QGIS hydrology tool. After filling the DEM, the flow direction was computed for every cell. Then flow accumulation was considered to generate the drainage network of the watershed. The watershed has been divided into the cells and coordinates of the central points of the cells were rectified in QGIS environment. Cell-wise average slope and dissection index were also calculated. For evaluating the watershed hydrogeomorphic characteristics, the selected parameters of the linear, areal and relief aspects have been extracted in QGIS considering the formulae propounded by the geomorphologists and hydrologists (Table 2).

Data Collection and Software Used

The distinct information and data required for the present study were procured from different sources, which were then imported to GIS environment. A brief review of data collection and GIS software is given in ensuing section. Basin length (Lb.) Maximum length of the basin measured parallel to the main drainage line Strahler (1964) [12] 3.

Stream length (Lu) Length of the Major stream Horton (1945) [5] 4.

Mean stream length (Lsm) Lsm = Lu / Nu, Lu = Total stream length of order 'u' Nu = Total no. of stream segments of order 'u' Strahler (1964) [12] 5.

Bifurcation ratio (Rb) Rb = Nu / Nu + 1, Nu = Total no. of stream segments of order 'u' Nu + 1 = Number of segments of the next higher order Schumm (1956) [8] 6.

Mean bifurcation ratio (Rbm) Rbm = Average of bifurcation ratios of all orders Strahler (1957) [11] 7.

Stream length ratio (Rl) Rl = Lu / Lu -1, Lu = The total stream length of the order 'u' Horton (1945) [5]

Lu -1 = The total stream length of its next lower order Arial Aspects 8.

Total Area (A) Total area of river basin ---9.

Drainage density (Dd) Dd = ∑Lu / A Horton (1932) [6] 10.

Stream frequency (Fs) Fs = ∑Nu / A Horton (1932) [6] 11.

Form factor (Rf) Rf = A / Lb² Horton (1932) [6] 12.

Circularity ratio (Rc) Rc = 4 A / P² Miller (1953) [7] 13.

Drainage texture (T) T= Dd × Fs Horton (1945) [5] 14.

Elongation ratio (Re) Re = 1.128√A / Lb Schumm (1956) [8] 15.

Length of overland flow (Lg) Lg = 1/2Dd Hoerton 1945 [5] Relief Aspects

16.

Basin Relief (R) R = H-h, H is maximum elevation and h is minimum elevation within the basin.

Dissection Index (DI) DI = R/Ra Singh S (1994) [9] 18.

Relief Ratio (Rr) Rr = R/Lb Scumm (1956) 19.

Ruggedness number (Rn) Rn = R × Dd R is the basin relief and Dd is the drainage density Strahler (1958) [13]

Results and Discussion

The results of morpgometric analysis of pingalgarh watershed VNMKV, Parbhani.

Linear Aspects of Pingalgarh watershed

In this present study, the linear aspects of Pingalgarh watershed consists of parameters like perimeter, stream order, stream number, stream length, stream length ratio and bifurcation ratio.

Perimeter (P):

The Perimeter of Pingalgarh watershed is 32.63 km.

Basin Length (Lb.): Lb measures geometrical size and shape of a drainage basin. Pingalgarh watershed has a Lb of 8.29 km Length of the Main Stream

Length of the Main Stream:

This in general denoted by length of the main stream. In the digitization procedure, the main channel length was digitized using ArcGIS-10.8 software. The analysis showed that the length of the main stream is 8.29 km.

Stream Order (Nu):

The first step towards drainage basin analysis is the designation of stream order which shows the relative and hierarchical relationship between stream segments, their connectivity and the discharge having contributions of the watershed (Figure 3). In the overall drainage of the basin area pattern of drainage comprises dendritic, parallel and trellis patterns since are constituted of network of various tributaries and its master stream which flows along the general slope direction which in turn are well adhered to the respective geological structures.

Stream Number (u)

Horton stated that the numbers of stream segments of each order eventually form an inverse geometric sequence with the order number. The total number of streams in the study area is 658 as mentioned above.

Stream Length (Lu)

The stream network of Pingalgarh watershed was previously categorized into several orders, which were then computed using "Measure" tool of Arc GIS software using DEM as primary data. The stream length according to the law proposed by Horton2 has been computed. The total length of streams (Lt) in Pingalgarh watershed is 181.52 km.

Bifurcation Ratio (Rb)

The bifurcation ratio can be defined as a ratio of the number of stream segments of given order to the number of segments of next higher order. Bifurcation ratio is a good index of relief and dissection. Values of Rb typically range from the theoretical minimum of 2.0 to 5.0. For the study area mean bifurcation ratio is 3.79 indicates that the geologic structures did not distorted or disturbed the drainage patteren.

Areal Aspects of Pingalgarh watershed

The areal aspects generally include various parameters like area, drainage density, drainage texture, stream frequency, form factor, circularity ratio, etc. It is found that size of the basin is inversely related to maximum flood discharge per unit area.

Area (A):

The Area of Pingalgarh watershed is 30.43 km 2 i.e 3043 Ha.

Drainage Density (Dd)

The drainage density has been found to be an important indicator of the linear scale of landform element in stream which is topographically eroded and is defined as a ratio of the total length of streams of all orders to its drainage area. The value of drainage density (Dd) is 3.94. The low drainage density is often found to be favored by highly permeable subsoil region bearing dense vegetation cover whose relief is low, whereas high drainage density always favored in regions having weak or impermeable sub-surface materials, sparse vegetation and high mountain relief (Figure 4). In the present study the drainage texture value of Pingalgarh watershed stands at 7.998, it indicates that the pattern of texture of Pingalgarh watershed is fine drainage texture.

Stream Frequency (Fs)

The value of stream frequency of Pingalgarh watershed found to be 8.57. Thus, the stream frequency falls under moderate frequency class in the study area (Fig. 5). The stream frequency found in the study area shows a positive correlation with its calculated drainage density, indicating an increase in the stream population with the increase in drainage density.

The Relief Ratio (Rr) of Pingalgarh watershed is 0.004 as shown in Table 4. Pingalgarh watershed has the lowest Rr value is 0.004 indicating with gentle slope and low relief.

Ruggedness Number (Rn)

The Ruggedness Number (Rn) of Pingalgarh watershed is 0.134. This indicates that the area is rugged with low relief and low stream density, as slopes are short and small.

Conclusion

This study shows that remote sensing techniques and the GIS play a crucial role in the timely and cost-effective preparation of drainage maps and morphometric analysis and the assessment of morphometric drainage parameters is more suitable than traditional ones. Mean bifurcation ratio value is estimated to be 3.790 shows that mean bifurcation ratio for entire basin is in the range of 3.0 to 5.0. The values of basin fall in the range of bifurcation ratio in which the geologic structures do not distort the drainage pattern. This study is useful in water and land resource development plan with the help of remote sensing and GIS techniques.

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