Physiography & Drainage
Jabalpur area is hilly and undulating in nature with elevations varying between 395 and 470 m above mean sea level (mamsl). The average elevation of GIF area is around 400 mamsl. However, the study area is relatively plain with gentle undulations at places. It is a part of the Narmada River basin and forms its upper reaches.
Hydrometeorology
Jabalpur’s climate is characterized by a hot summer and general dryness except during the South West (SW) monsoon period (June to September). October and November form the post monsoon period. The average annual rainfall is 1461 mm of which about 90% (1315 mm) falls during the monsoon season. While the maximum mean monthly rainfall is 467.50 mm (July), the minimum mean monthly rainfall is 4 mm (December) with number of rainy days in a year varying between 62 to 120 days. The cold season starts from December (min. 9.7oC) to February and is followed by the hot season from March to about the middle of June (max. 42oC).
Hydrogeology
Hydrogeology of GIF area is mainly controlled by the geomorphological and geological setup and also by climatic conditions. The area is underlain by a consolidated formation comprising of granites and granite gneisses of Mahakausal Group of Precambrian age. The granites are coarse grained, hard, massive and pinkish in colour. The water yielding capacity of these rocks largely depends on the extent of weathering, fracturing, openness and size of fractures and extent of their interconnection with the near surface weathered zones. These interconnected joints and fractures in the underlying hard rocks facilitate circulation of groundwater and in turn form deeper aquifers.
There are about 6 borewells constructed inside GIF premises. About half of them are production wells. Three borewells, as listed in Table 1, were selected to measure the depth to water levels (DTW). On August 21, 2916 the DTW varied between 0.7 and 1.81 below ground level (mbgl) while on October 20, 2016 during postmonsson season, it was between 2.6 to 3.35 mbgl.
Table 1
Depth to water level in Grey Iron Foundry premises, Jabalpur, India.
S. No. | Location | Depth to water level (mbgl |
21.08.2016 | 20.10.2016 |
1 | BW – 1 near Main Gate | 1.81 | 3.2 |
2 | BW − 2 near Fetling Shop (Bld. No.2) | - | 3.35 |
3 | BW − 3 near Pattern Shop (Bld. No.3) | 0.7 | 2.6 |
Feasibility of Rooftop Rain Water Harvesting: The DTW in GIF premises is too shallow for injection of groundwater into the aquifers through rooftop rainwater harvesting since there are chances that the injected recharge will be rejected by the aquifers during the monsoon season. Therefore, the rain water collected during the rainy season has to be stored either by an underground or on-the-ground cemented structure of adequate volume.
Grey Iron Foundry desired that roof top rain water harvesting be practiced in their Building Nos. 1, 2 and 3 initially. Dimensions of these buildings are given in Table 2. It is estimated that an amount of about 21,784 m3 of collected rain water is available for storage from these buildings (Table 2). Calculations for individual buildings are shown in the table. The collected rain water has to be stored in storage tanks.
Table 2
Rain water available in three buildings of Grey Iron Foundry, Jabalpur, India for rooftop rain water harvesting.
Sl. No. | Location | Roof Area (m2) (1) | Annual rainfall (m) (2) | Maximum rainfall in 15 min. (m) (3) | Runoff coefficient (0.8*0.85 = 0.68) (4) | Total water collected from roof in a year (m3) (1*2*4) | Maximum water collected from roof in 15 min. (m3) (1*3*4) | Capacity of settling tank (m3) (1*3* 0.85) | Dimensions of settling tank (m) | Dimensions of storage tank (m) |
1 | Building No. 1 | 9487 | 1.461 | 0.03 | 0.68 | 9425.1 | 193.5 | 241.9 | 12 x 6 x 3.5 | 5 x 50 x 50 |
2 | Fetling Shop (Building No. 2) | 9100 | 1.461 | 0.03 | 0.68 | 9040.7 | 185.6 | 232.1 | 12 x 6 x 3.5 | 5 x 50 x 50 |
3 | Pattern Shop (Building No. 3) | 3339.6 | 1.461 | 0.03 | 0.68 | 3317.8 | 68.1 | 85.2 | 7 x 4 x 3.5 | 5 x 30 x 28 |
| Total | 21926.6 | | | | 21783.6 | 447.2 | 559.2 | | |
Note: Runoff coefficient for the galvalume sheets = 0.85; Coefficient for evaporation, spillage and fist flush etc. = 0.80 (CPWD, 2002). |
Building Nos. 1 and 2 require a volume space of 10,000 m3 individually for storing rainwater when the annual rainfall is normal, i.e., 1461 mm. For higher rainfall extra volume shall be required since annual rainfall in the area often goes beyond 1500 mm (CWC, 2014). Therefore, it would be safe to make provision for a volume space of 12,500 m3 (i.e., 25% extra). The dimensions for the underground/on-the-ground tanks to hold this volume of water in individual building shall be (5 x 50 x 50) m, if the height of the tanks shall be kept at 5 m. Dimensions could be changed depending on convenience. If GIF so desires, two different tanks can be constructed for each of these two buildings if sufficient space for one single tank for a building is not available.
For Building No. 3, a storage volume space of 3340 m3 is required for the normal rainfall of 1461 m. For safety, provision may be kept for a volume space of 25% extra. So, the desired volume of the tank, underground or on-the-ground, should be in the order of 4200 m3 with dimensions of (5 x 30 x 28) m or (4 x 30 x 35) m or other suitable dimensions depending on availability of space. In this case too, the tank volume could be halved into two for two different tanks of the desired volumes if site conditions do not allow to construct one single tank.
Collected roof water is expected to have some amount of silt or other suspended materials in it. Therefore, before the collected rainwater enters into these storage tanks, provision has to be kept for settling tanks for silts in roof water to settle down. A duration of 15 minutes is good enough for this purpose. Therefore, the size of these settling tanks should be such that they should be able to hold collected rainwater for a period of at least 15 minutes. Maximum rainfall intensity of 30 mm (0.03 m) in 15 min is assumed for Jabalpur while estimating the volume of the settling chambers. Accordingly, the dimensions of the settling tanks may be kept at (12 x 6 x 3.5) m for Building Nos. 1 and 2 and (7 x 4 x 3.5) m for Building No. 3. (Table 2).
The current designs of the buildings are such that down-take pipes are already existing in all buildings, except the northern side of Building No. 2, where provision for such down-take pipes has to be made. Therefore, what is required in each building is to make arrangements to collect rainwater from these down-take pipes and bring it to one channel through pipeline of adequate diameter and connect to the respective settling chamber and then the storage tank. A rough design of the collection and storage system is shown in Fig. 1. The rain water thus stored could be used for multiple purposes by making suitable arrangements.
The foundry requires about 640 m3 of drinking water and 70 m3 of raw water for cooling purposes on daily basis (reported by GIF). Thus, the annual requirements for cooling purposes are estimated at 25,550 m3, while total rain water that could be stored by these tanks is about 21,784 m3, which is 85% of the cooling water requirements.
Chemical Quality of Groundwater
Chemically, concentrations of the groundwater quality parameters, except that of Fluoride, lie within the standards prescribed by the Bureau of Indian Standards (BIS, 2012) for drinking purposes (Table 3). The BIS acceptable limit for Fluoride is 1.0 mg/L, while the maximum permissible in the absence of an alternative source is 1.5 mg/L. Its source in this area could be from the weathered granite formations. However, its persistence and seasonal variations need to be further examined. Under the present circumstances, the groundwater is not suitable for drinking due to presence of excessive amount of Fluoride in it. The rainwater collected at GCF 6 km away from GIF is slightly acidic in nature (Naik et al., 2022) and lacks all constituents desired of potable water.
Table 3. Chemical quality of groundwater in Grey Iron Foundry, Jabalpur, India.
S. No.
|
Location
|
Source
|
pH
|
EC
|
CO3
|
HCO3
|
Cl
|
F
|
SO4
|
Na
|
K
|
Ca
|
Mg
|
TH
|
|
in µS /cm
|
<------------------Concentrations in mg/L------------------------>
|
1
|
Inside GIF premises
|
Borewell
|
8.06
|
405
|
0
|
195
|
35
|
2.3
|
13
|
29.9
|
2.8
|
40
|
10.8
|
145
|
2
|
GIF Main Gate
|
Borewell
|
8.37
|
428
|
0
|
220
|
28
|
3.0
|
15
|
32.3
|
1.5
|
52
|
8.4
|
165
|