X = 3.73
Here, A = Lowest Value = 177.99
B = Highest Value = 122.04
n = Number of Class = 5
X = Class Interval
The lowest value is 122.04 and the interval is 3.73
Now, the 1st range will be = 122.04-----125.77 (122.04 + 3.73 = 125.77)
The second range will be = 125.77-----133.23 (125.77+(2*3.73))
The third range will be = 133.23-----144.42 (133.23+(3*3.73))
The fourth range will be = 144.42-----159.34(144.42+(4*3.73))
The fifth range will be = 159.34-----177.99 (159.38+(5*3.73))
Finally, among the two procedure of frequency distribution, the well-suited one for our study will be selected. The values of skewness from the method of equal class interval is -0.901 and by arithmetic mean method is -2.064. The acceptance of class interval depends on how close the value of skewness from zero 0. Skewness value nearer 0 means the data are more normally distributed. The value of equal class interval is nearer to zero than the arithmetic mean method. Therefore, the equal class interval method will be used for ranging data for choropleth map.
Analysis: Total 64 districts of Bangladesh has been categorized into five categories. The considered five regions has been grouped as very low availability of water, moderately low availability of water, medium availability of water, moderately high availability of water, very high availability of water.
Range of composite score | Attribute | Frequency | Percentage | District |
122.04-133.23 | Very low availability of water | 2 | 3.125% | Bandarban, Rangamati |
133.23-144.42 | Moderately low availability of water | 1 | 1.56% | Khagrachhari |
144.42-155.61 | Medium availability of water | 17 | 26.56% | Narail, Meherpur, Chandpur, Chapai nawanganj, Manikganj, Lalmonirhat, Khulna, Panchagarh,Chuadanga, Thakurgaon, Magura, Joypurhat, Shariatpur, Rajbari, Gopalganj, Narshingdi. Munshiganj |
155.61–166.80 | Moderately high availability of water | 32 | 50% | Natore, Madaripur, Maulvibazar, Cox'sBazar, Gazipur, Kurigram, Sunamganj, Kushtia, Dhaka, Sirajganj,Narayanganj, Faridpur,Jamalpur, Jhalikathi, Jhenaidah,Gaibandha, Brahmanbaria, Bhola, Rangpur, Nilphamary, Satkhira,Bagerhat, Sherpur, Habiganj, Pabna, Naogaon, Kishoreganj, Dinajpur, Pirojpur, Tangail, Netrokona, Jessore. |
166.80-179.99 | Very high availability of water | 12 | 18.75% | Bogra, Sylhet, laxmipur, Rajshahi, Barisal, feni, noakhali, patuakhali, Comilla, Chittagong, Mymensingh, barguna |
,
Regions of very low availability of water: Among the 64 districts of Bangladesh, only 2 regions show the low availability of water. Almost 3.125% is in this category. The regions name bandarban and Rangamati are in this group. Rangamati and Bandarban both districts are located Chittagong hilly tracts at south eastern side of Bangladesh. In these regions, the temperature is relatively high and rising day by day. Water table see a gradual fall due to rise in temperature. This is one of the main reasons of water scarcity. On the other hand, the number of total cultivable land is higher is these regions. This is the other main reasons of water scarcity in these regions.
Regions with moderately low availability of water: In between the 64 total administrative areas in Bangladesh only Khagrachhari has moderately low availability of water. It covers almost 1.56% are categorized in this group. The region lies in this group is a hilly region which is located in Chittagong hilly tracts. The ground water level is low in this region due to high rising temperature which tends to water scarcity. The average temperature is lower than the other two region of Chittagong hilly tract and the number of water bodies are also high than those regions lying in low water availability regions.
Regions with medium availability of water: Around 26.56% districts of Bangladesh are in medium availability of water. The regions are Narail, Meherpur, Chandpur, Chapai nawabganj, Manikganj, Lalmonirhat, Khulna, Panchagarh, Chuadanga, Thakurgaon, Magura, Joypurhat, Shariatpur, Rajbari, Gopalganj, Narshingdi, Munshiganj. These regions specially narail and Magura and Rajbari, has higher temperature and low precipitation rate. Due to the high temperature, the water availability in those regions are medium. The region Chapai nawabganj has the lowest temperature, the number of water bodies are also low in this region and the water table is also going down day by day. These tends to the water scarcity in this region. Meherpur,, Khulna, Panchagarh, Chuadanga, Thakurgaon, Magura, Shariatpur, Rajbari, Gopalganj, Munshiganj rainfall and temperature of these regions remains moderate. Though Meherpur, Panchagarh, Chuadanga, Thakurgaon, Gopalganj has lower temperature than other the number of water bodies are higher in these regions. The other regions of this category have moderate temperature and rainfall.
Regions with moderately high availability of water: All around 50% districts are categorized in this group. All about half of the regions of Banlgadesh are categorized here. The regions categorized in this group are Natore, Madaripur, Maulvibazar, Cox'sBazar, Gazipur, Kurigram, Sunamganj, Kushtia, Dhaka, Sirajganj,Narayanganj, Faridpur, Jamalpur, Jhalikathi, Jhenaidah,Gaibandha, Brahmanbaria, Bhola, Rangpur, Nilphamary, Satkhira,Bagerhat, Sherpur, Habiganj, Pabna, Naogaon, Kishoreganj, Dinajpur, Pirojpur, Tangail, Netrokona, Jessore. The regions such as pabna, naogaon, dinajpur, sirajganj, Rangpur, natore, Nilphamary are lied in the northern part of Bangladesh. They face drought and high raised temperature in every summer even their water level goes down in those seasons. There is also less amount of precipitation in these regions. Though these regions lies in the northest part of Bangladesh where there remains the higher temperature, precipitation and extreme drought the number of water bodies are higher in these region and they have lower number of cultivable lands that’s why these regions are categorized in moderately high available of water. The temperature of Jhenaidah and Jessore also remains high now a day but they have higher number of water bodies. This is the reasons of their moderately water scarcity. The other regions which are close to Dhaka city also lies in this group. The main reasons of water scarcity in this region are increased human consumption, over use and wastage of water, over use of aquifers and its consequent slow recharge. These all reasons are responsible for water scarcity. The other regions jhalokathi, bhola,shatkhira and Bagerhat faces water scarcity due to natural calamities such as storm, floods.
Regions with very high availability of water: All around 18.75% districts are categorized in this group. There are different reasons of water unavailability in these regions. The regions which are grouped in this category are Bogra, Sylhet, laxmipur, Rajshahi, Barisal, feni, noakhali, patuakhali, Comilla, Chittagong, Mymensingh, Barguna. In Sylhet, the temperature remains low and there is a high rate of precipitation. This tends to water availability. In Mymensingh the water availability is high due to high precipitation rate and low temperature and huge number of waterbodies. Though rajshahi and bogra lies in the northern part of Bangladesh the water availability is high in this region due to the huge number of water bodies and the low number of cultivable land. In Chittagong, the precipitation rate is very much higher than the other regions this tends to higher water availability. Barishal and patuakhali are reached with water bodies which tends to a good potential for water availability.
Conclusion: After delineating the region it is clear that the overall water condition of Bangladesh varies. The condition varies from district to district. Some districts are well improved. On the other hand, some districts still lacking the water. The key reasons of this water unavailability is precipitation rate, temperature, their geographical positions and topographical characteristics. This particular study finds that the mostly region lies in Moderately high availability of water category. Almost 50% of the districts are in this group. The region of bandarban, Rangamati and khagrachari are the lowest regions of water availability. Due to their topographical condition, the water level remains low there and these regions have low number of water bodies. Almost 18% of the regions are zoned in highly water availability region. The regions named Bogra, Sylhet, laxmipur, Rajshahi, Barisal, feni, noakhali, patuakhali, Comilla, Chittagong, Mymensingh are in this region. To mitigate the delination among all those regions the government and respective authority should take proper steps.