study of spatial and temporal distribution of rainfall in ... suitable measures for mitigating the...

INTERNATIONAL JOURNAL OF GEOMATICS AND GEOSCIENCES

Volume 2, No 3, 2012

© Copyright 2010 All rights reserved Integrated Publishing services

Research article ISSN 0976 – 4380

Submitted on January 2012 published on February 2012 712

Study of spatial and temporal distribution of rainfall in Nagaland (India) Kusre B.C, Singh Kh.S

College of Agricultural Engineering and Post Harvest Technology; Central Agricultural University; Ranipool, (E) Sikkim- 737135

[email protected]

ABSTRACT

Cropping system of a region is decided by and large, by number of soil and climatic parameter which determines overall agro-ecological setting for nourishment and appropriateness of a crop or set of crops for cultivation. Rainfall is one of the important climatic parameter influencing the cropping pattern, productivity, flooding and drought hazards, erosion and sedimentation. It is therefore necessary to study the spatial and temporal variation of rainfall for judging the agricultural production potential and sustainability of agricultural production system. However, rainfall has one the highest spatial-temporal variability especially in mountain region where in addition, there is scarcity of information. Planning suitable measures for mitigating the problems requires through knowledge of the rainfall pattern.The present study was taken up to analyze the spatial and temporal variation of rainfall in Nagaland state of India. The state is mainly dependent on agrarian economy and thus knowledge of rainfall distribution in space and time is of significance for agricultural planning. The analysis of rainfall showed that there exists a wide variation in the rainfall amounts with variation from 859 mm to 2123 mm. Annual rainfall pattern indicates that northern part receives higher rainfall as compared to eastern and western side of the state. Similarly for July and monsoon season northern side receives higher rainfall. However, during December, Northern side receives less rainfall as compared to eastern and western part of the state.

Keywords: Spatial, temporal, rainfall variability, Theissen polygon.

1. Introduction

Cropping system of a region is decided by and large, by number of soil and climatic parameter that determines overall agro-ecological setting for nourishment and appropriateness of a crop or set of crops for cultivation (Das, 2006). Rainfall is one of the important climatic parameter influencing the cropping pattern, productivity, flooding and drought hazards, erosion and sedimentation. Irrigated system also requires rainfall to replenish surface water or the aquifers. An understanding of the spatial distribution is of paramount importance for judging the agricultural production potential of a region and hence, the sustainability of agricultural production system in a given area (Gòbel et al., 1996). However, rainfall has one the highest spatial-temporal variability especially in mountain region where in addition, there is scarcity of information. Knowledge of spatial and temporal rainfall pattern is necessary for planning suitable measures for mitigating the problems. Three main characteristics of rainfall are its amount, frequency and intensity, the values of which vary from place to place, day to day, month to month and also year to year. Precise knowledge of these three main characteristics is essential for planning its full utilization (Dastane, 1978). The rainfall characteristics also vary during various parts of the year and each has its significance influencing the cropping pattern.

Study of Spatial and Temporal Distribution of Rainfall in Nagaland (India)

Kusre, B.C, Singh, Kh. S

International Journal of Geomatics and Geosciences

Volume 2 Issue 3, 2012 713

The Geographical Information System (GIS) is an effective tool for mapping the spatial distribution and its trend. GIS have been used worldwide by number of researchers for spatial mapping. GIS is a system for capturing, storing, checking, integrating, manipulating, analyzing and displaying data which are spatially referenced to the Earth, fall in to this category (DE, 1987). It produces intelligent data that supports analyses and allows display of tabular and spatial information to assist decision-makers (Kaijuka, 2007). GIS can provide a key set of components needed for planning in the form of geo-referenced data (Mustafa et al., 2005). Sarma (2005) analyzed the spatial distribution pattern of annual, monsoon and non monsoon rainfall in the coastal zone of Andhra Pradesh. Similarly Vennila (2007) studied the rainfall variation in the Vattamalaikarai sub basin in Tamil Nadu. In another study conducted by Rathod and Aruchamy (2010) spatial analysis of rainfall variation in Coimbatore District of Tamil Nadu using GIS tool. Similarly, the present study is made to understand the spatial variation of different data series such as annual, monsoon, arrival of monsoon, July and December month rainfall for the state of Nagaland. Each of the data series has its importance in terms of planning sowing and harvesting time, arrangement of life saving irrigation, planning suitable soil and water conservation measures and others.

By studying the spatial-temporal rainfall of Nagaland with a simple yet direct approach, we hope to generate information for the decision makers and farmers. With the help of such information better planning can be done for enhanced agricultural productivity with available resources in the absence of extensive expertise.

2. Description of the Study Area

Nagaland is a constituent state of North East India located between latitudes of 25˚06' to 27˚04' N and longitudes of 93˚21' to 95˚15' E. The area covered by the state is 1.66MHa. The total percentage of the area as compared to India is 0.50%. The state is bounded by Assam in the north and west; Myanmar and Arunachal Pradesh in the east and Manipur in the south. The state is administratively divided into 11districts namely; Kohima, Phek, Wokha, Zunheboto, Mokokchung, Tuensang, Longleng, Peren, Kiphire, Dimapur and Mon. Figure 1 show the state of Nagaland and its districts. The physiography of the state is characterized by elevated ridges and intermountain valleys. The topography of the state is highly undulating with elevation varying from 160 m to 3841 m above mean sea level. In Nagaland state 72 soil families were identified.

The average annual rainfall of the state varies from 859.97 mm to2123 mm. More than 60.73% of rainfall occurs during monsoon i.e. June to September. Average annual temperature ranges from 18-20˚C for higher altitudes and 23-25˚C for lower altitudes.

Rice is the stable food crop of Nagaland state. Jhum cultivation is the traditional farming system in the Nagaland state. Maize, Millets and vegetables are grown on hills slopes and rice is cultivated in hilly terraces. The total area under agriculture in the state in 2009 was 0.39 Mha, out of this, 0.34 Mha is under traditional cultivation including Jhum paddy cultivation, Terrace paddy cultivation, maize, oil seed and pulses cultivation. The area under paddy cultivation is 0.174 Mha. The area under commercial crops cultivation is about 0.043 Mha and cultivation of other cereals is about 0.0061 ha.

The majority of the income can be attributed to agriculture; consequently, the importance of the timing and amount of rainfall that occurs in Nagaland cannot be overstated. Land and agriculture are the primary resources of the state for sustenance of the people and economy. Large scale industrialization or commercialization is still in the initial stages. It can therefore





be implied that agriculture and allied sectors need to be accorded special attention for states development and economy (NIC, 2011). The state is mainly dependent on rainfed agriculture with jhum cultivation as predominant practice.

3. Methodology

The rainfall data for 15 stations were collected from the Department of Soil and Water Conservation, Government of Nagaland (Table 1). The locations of the stations were plotted on the map of Nagaland using Arc GIS platform (Figure 1). The processing of rainfall data was performed by converting it into various data series such as annual, monsoon, arrival of monsoon, July and December months. The statistical behaviors of any hydrological series can be described on the basis of mean, standard deviation, coefficient of skewness and coefficient of kurtosis taken as measure of variability.

Spatial coverage of each rainfall station was performed by constructing the Thesissen’s polygon map using proximity analysis module in Arc GIS. The spatial coverage maps for each data series were prepared using spatial interpolation techniques available spatial analyst module in Arc GIS.

4. Results and Discussion

The outcome of the study revealed various facts about the spatial-temporal variation of rainfall in the state. The variation included in different data series such as mean annual, onset of monsoon, rainfall in the month of July and December and in the monsoon season. The results of each series are discussed below:

4.1 Variation in mean annual rainfall

The variation of mean annual rainfall was studied for the state (Table 2). An isoheytal map was created through interpolation techniques in Arc GIS 9.3 platform. The analysis showed that highest rainfall is mostly concentrated in the northern part of the state. The eastern and western boundaries receives relatively lower amount of rainfall. A strip bisecting the state receives moderately higher rainfall (Figure 2).

Table 1: The details of the rainfall station and the length of data for each station

Sl

No

Name of Station Latitude

(N)

Longitude

(E)

Altitude

(m)

No of years

1 Bhandari 26.28 94.13 703 8

2 Dimapur 26.83 93.69 160 7

3 Jalukie 25.66 93.68 415 8

4 Kiphire 25.97 94.78 1195 8

5 Kohima 25.65 94.12 1420 29

6 Meluri 25.69 94.93 1350 8

7 Mon 26.72 95.03 734 7

8 Phek 25.73 94.47 1360 7

9 Sechu 25.72 94.04 1094 12

10 Wokha 26.10 94.26 1360 7

11 Zunheboto 26.24 94.51 1780 7





12 Mokokchung 26.33 94.52 1180 6

13 Tsemenyu 26.92 94.92 1200 5

14 Mongkolemba 26.50 94.64 661 5

15 Tuensang 26.20 94.82 1480 4

Table 2: Average Annual Rainfall of all the 15 stations for which data was available

Sl. No. Name of the

Stations

Average annual

Rainfall (mm)

Elevation

(m)

Standard

Deviation

Coefficient of

Variation

1 Kohima 1772.34 1420 359.67 0.20

2 Bhandari 1772.11 703 483.66 0.27

3 Dimapur 1211.05 160 161.06 0.13

4 Jalukie 1417.13 415 221.17 0.16

5 Kiphire 859.971 1195 195.38 0.23

6 Meluri 1125.91 350 248.76 0.22

7 Mon 1893.28 734 285.39 0.15

8 Mokokchung 1765.64 1180 502.42 0.28

9 Phek 1588.38 1360 167.10 0.11

10 Sechu 1852.83 1094 317.01 0.17

11 Tseminyu 1509.20 1200 265.47 0.18

12 Tuensang 1328.40 1480 127.53 0.10

13 Mongkolemba 2012.92 661 404.02 0.20

14 Wokha 2123.43 1360 486.50 0.23

15 Zunheboto 1514.35 1780 853.18 0.56

Figure 1: Map of Nagaland showing Districts and the rainfall station





Figure 2: Map of Nagaland showing Theissens Polygon and distribution of annual rainfall (m)

Highest annual average rainfall in the state varies from 859.97 at Kiphire to 2123.43 mm at Wokha. This indicates that there exists a wide variation of rainfall distribution in the rainfall in the state. The rainfall pattern in the state was further divided into five categories Very high rainfall zone, moderately high rainfall zone, high rainfall zone, medium rainfall zone and low rainfall zones. In general the northern part received very high rainfall.

1. Very high rainfall zone (1817-2122 mm): The stations falling under this category are Sechu, Mon, Mongkolemba and Wokha.

2. Moderately high rainfall zone (1634-1817 mm): The stations under this category are Mokukchung, Bhandari and Kohima

3. High Rainfall zone (1438-1634 mm): The stations under this category are Tseminyu, Zunheboto and Phek

4. Medium rainfall zone (1233- 1438 mm): The stations under this category are Tuensang and Jalukie

5. Low rainfall zone (860-1233): Kiphire, Meluri and Dimapur

The coefficient of variation of annual variation for each station varied from 0.11 to 0.56. Effort was made to study the variation of rainfall with the altitude. It was found that there exists no relation between the elevation of the stations and rainfall received by each station. The state of Nagaland is hilly with a wide ranging topography. The localized effect may be the reason for such rainfall variation.





4.2 Monthly rainfall distribution pattern

The average monthly rainfall of 15 stations for Nagaland indicated that there exists a rainfall variation in each month. The average annual rainfall increases January to July and there is decline (Figure 3). Month of July receives highest average rainfall (287.68 mm) and the month of December receives the minimum with an average of 13.40 mm. Amongst the various stations the rainfall received for the month of July varied from 405.60 mm for Wokha to 183.13 mm in Kiphire.

The spatial variation for the month of July and December was studied (Figure 4 and Figure 5). It was found that during the month of July the Northern part of the state receives higher rainfall as compared to the East. However, the month of December indicates that the rainfall in the northern region is less as compared to other part of the state.

Figure 3: Distribution of average monthly rainfall pattern in Nagaland

4.3 Average weekly rainfall distribution

The average weekly rainfall distribution pattern for all the 15 stations was studied. It was found that in general pre-monsoon showers are received during 9th week of the year. As per Indian Meteorological Department (IMD), the arrival of normal monsoon in the state begins during 1st of June coinciding with the 21st calendar week. The variation average rainfall during the 21st week was studied (Figure 6). The rainfall during 21st week also had major concentration in the northern part of the state. The eastern side of the state indicates lesser amount of rainfall during 21st week of the year.

4.4 Seasonal rainfall variation

The seasons in Nagaland can be broadly classified as pre monsoon (March-May), Monsoon (June-September) and Post monsoon (October to February). It was found that 60.73% of





rainfall is received during monsoon. In the post monsoon period the rainfall quantity falls to 12.17% (Table 3). The distribution of monsoon season rainfall in the state was studied for the state (Figure 7). The distribution pattern indicates heavy rainfall amount in the northern and in the central part of the state.

Table 3: Seasonal rainfall pattern of Nagaland

Parameters Pre monsoon Monsoon Post monsoon

Average Rainfall amount 430.36 961.44 192.67

Percentage of rainfall 27.1 60.73 12.17

Standard deviation 68.99 65.17 44.53

Coefficient of variation 17.99 8.05 23.11

4.5 Agricultural Planning in Nagaland based on rainfall distribution

It has been reported that rice and maize are the major crops in Nagaland (Tiwari et al., 2010). Rice is grown in around 16.5 thousand hectare of the state and the productivity is 1.699 t/ha as against national average of 1.667 t/ha. The cultivation of rice requires ploughing thoroughly and puddled with 3-5 cm of standing water in the field. The optimum depth of puddling is found to be around 10 cm in the clay and clay-loam types of soils. The primary objective is to obtain a soft seedbed for the seedlings to establish themselves faster, to minimize the leaching losses of nutrients and thereby increase the availability of plant nutrients by achieving reduced soil conditions which facilitates a better availability of nutrient elements, to incorporate the weeds and stubble into the soil and to minimize the weed problem. Therefore a good rainfall is necessary for paddy cultivation. Sowing of maize is generally taken up 10 days before onset on monsoon. In regions with about 60 cm of well-distributed rainfall during the growing season, any additional irrigation is not necessary. Inadequate soil moisture during flowering and post-flowering particularly during the grain-filling period will markedly reduce the yield (Krishi World, 2011). In Nagaland combination of Rice Maize cultivation is also practiced.

The analysis showed that good average weekly rainfall (> 16 mm) starts from 12th week when primary tillage practice can be initiated in the state. On 15th week sowing of summer Maize may be done and 22nd week can be ideal for paddy when rainfall is more than 100 mm. The 29th week is ideal time for initiation of wetland preparation for short duration paddy. This paddy can be harvested before the recession of monsoon. In the post monsoon season, the residual moisture can be utilized for potato and vegetable cultivation.

Apart from the above crops such as potatoes and vegetables are also grown in the state. The productivity of vegetable is around 11.3 t/ha against the national average of 15.2 t/ha (IHB, 2001). Proper crop planning can improve in productivity of some of the major crops of the state. These crops are generally taken during the Rabi season viz., in the post monsoon season. As these crops require lesser amount of water, the December month distribution was also studied and its spatial distribution is also analyzed.

The state of Nagaland is also known for cash crops like tea and coffee. The pre monsoon showers during March and April are useful for initiation of tender leaf which also aids to good quality produce.





Figure 4: Map of Nagaland showing distribution of average July month rainfall (mm)

Figure 5: Map of Nagaland showing distribution of average December month rainfall (mm)





Figure 6: Map of Nagaland showing distribution of average 21st week rainfall (mm)

Figure 5: Map of Nagaland showing distribution of average monsoon rainfall (mm)





5. Conclusion

The present study was conducted to study the spatial and temporal variation of rainfall in Nagaland. The specific conclusions of the study are shown below

1. The study revealed that although the average rainfall in the state high (1583 mm), but there is a wide spatial variation for all data series.

2. The entire state can be divided into five groups based on their average annual rainfall distribution.

3. The study of various data series viz., annual, weekly, seasonal and monthly indicated that northern part of the state receives higher annual, monsoon and July month rainfall. However, during December, the eastern and the western part of the state receive higher rainfall.

4. Normally 12th week is ideal for taking up primary tillage practice. Sowing of summer maize can be taken up in 15th week and 22nd week can be considered ideal for taking kharif paddy.

5. The 29th week is ideal time for initiation of wetland preparation for short duration paddy. This paddy can be harvested before the recession of monsoon.

6. In the post monsoon season, the residual moisture can be utilized for potato and vegetable cultivation.

6. References

1. Das, P., (2006), Cropping pattern (Agricultural and Horticultural) in different zones, their average yield in comparison to national average/ critical gaps/ reason identified and yield potential, In Government of India, Ministry of Agriculture, Department of Agriculture and Cooperation (Ed), Status of Farm Mechanization in India, pp 33-47, New Delhi, IASRI.

2. Dastane, N.G., (1978), Effective rainfall in irrigated agriculture, FAO Irrigation and Drainage Papers, Version 25, http://www.fao.org/docrep/X5560E/X5560E00.htm

3. DE, (1987), Department of Environment, Handling Geographical Information. Report of the Committee of Enquiry chaired by Lord Chorley. HMSO, London.

4. Gòbel, W., Ouali, A.El., Singh, M., (1996), Spatial interpolation of precipitation data: a example from Turkey, Workshop on Spatialization. E.U. Coastand Mètèo, France, pp 24-25 September, Toulouse, France.

5. IHB, (2001), Indian Horticultural Data base, National Horticultural Board, Ministry of Agriculture, Government of India.

6. Kaijuka, E., (2007), GIS and Rural Electricity Planning in Uganda, Journal of Cleaner Production, 15, pp 203-217.

7. Krishi World, (2011), Field Crops, www.krishiworld.com accessed on 30.11.2011.





8. Mustafa, Y.M., Amin, M.S.M., Lee, T.S., Shariff, A.R.M., (2005), Evaluation of Land Development Impact on a tropical Watershed Hydrology Using Remote Sensing and GIS. Journal of Spatial Hydrology, 5(2), 16-30.

9. NIC., (2011), http://nagaland.nic.in/planning&coord/Development%20Indicator.htm, 22dec, 2011.

10. Rathod, I.M, Aruchamy S., (2010), Spatial analysis of rainfall variation in Coimbatore District, Tamil Nadu using GIS, International Journal of Geomatics and Geoscience, 1(2), pp 106-118.

11. Sarma, V.V.J., (2005), Rainfall pattern in the coastal zone of Krishna Godavary basin Andhra Pradesh India, Journal of Applied Hydrology, 28(2), pp 1-11.

12. Tiwari, S.C., Sashi, S., Achrya, L., (2010), Agro biodiversity Potential of Nagaland State, north eastern India, Indian Journal of Traditional Knowledge, 9(2), pp 350-354.

13. Vennila, G., (2007), Rainfall variation analysis of Vattamlaikarai sub basin, Tamil Nadu, Journal of Applied Hydrology, 20(3), pp 50-59.

study of spatial and temporal distribution of rainfall in ... suitable measures for mitigating the...

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