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Geoscience e-Journals





An International Year of Planet Earth-2008 Initiative

Current Issue Technical

Year 2021

Volume 14 (1)

Accuracy of Rainfall Time Distribution Curves in Literature for a Coastal Site near Mumbai, India
Harshanth R.1,2, Saha Dauji2,3* and P. K. Srivastava3

The rainfall data is available for India majorly as 24-hour records, taken between 08:30 hours on consecutive days. Indian Meteorological Department (IMD) is establishing continuous recording rain gauge network, but sufficient sub-daily data would become available only after a few decades. Consequently, practicing engineers resort to generic time distribution curves to obtain sub-daily rainfall. Time distribution curves for rainfall available for India includes Central Water Commission-Indian Meteorological Department-Ministry of Surface Transport (CWC-IMD-MoST) curves for various zones and IMD-CWC curves for few river basins, respectively. Time distribution curves of rainfall are also available in international literature, namely, Standard Project Storm (SPS) and Technical Report No. 55 (TR55), both developed for USA. In this article, all these curves are evaluated for accuracy at a coastal site near Mumbai, India, which predominantly receives south-west monsoon rainfall. From the study, it is concluded that whereas SPS (index rainfall: 8 inches) and TR55 curves would, in general, provide safe (though uneconomic) design, adoption of SPS (index rainfall: 20 inches) curve, CWC-IMD-MoST curve (subzone 5a & 5b) or IMD-CWC curve for Catchment No. 102 for west flowing rivers would result in unsafe hydraulic design for this site. The deviations could be attributed to different rainfall characteristics at foreign locations or due to temporal, areal and ensemble averaging for the river basins in India. Rather than adoption of generic curves from literature, site specific time distribution curve for rainfall would be preferable for safe and economic design of important hydraulic structures.

Keywords: Time distribution of rainfall, Tropical rainstorm, Site-specific rainfall, Design storm
Seasonal variations in Microbial Diversity in Tropical Dry Deciduous Forest of Central Uttar Pradesh
Naushi Anis and Ajay Kumar Arya*

A study was carried out to examine the regular changes in the nutrient status under different land utilizes of tropical deciduous forest of Central Uttar Pradesh. Dry tropical soils were examined to analyses the seasonal dynamics of microbial biomass carbon, phosphorus and nitrogen. Other soil properties like pH, total organic carbon, total nitrogen, available phosphorus exhibit strong seasonality and comparatively they are higher in forest soils as compared to agricultural soils. At all the sites, the maximum MBC, MBN and MBP occurred during the dry period (summer season) and the minimum in wet period (rainy season).  Increased demand for plant nutrients during the rainy season reduced the supply of nutrients to soil microbes and thus low microbial biomass C, N and P. In the present study soil MB-C, MB-N and MB-P were higher at forest sites as compared to agricultural sites. Such findings suggest that the preservation of nutrients by soil microbial biomass was better in the limited logging stand which will lead to the recovery of forest under conservation. The differences in MBC, MBN and MBP were significant (P <0.001) among sites and seasons. The MBC (P < 0.0001), MB-N (P < 0.001) and MB-P (P < 0.0001) were positively correlated with organic C. Therefore, the minimum and maximum microbial biomass C, N and P during the rainy and winter season indicate a balance between a nutrient demand for plant growth and nutrient retention in microbial biomass that will help to recover the environment after disruption.

Keywords:  Forest, Organic Carbon, Disturbed sites, deforestation, dry period, wet season
Assessment of Water Quality of Nainital Lake and surrounding Springs, using Water Quality Index (WQI) and Heavy Metal Pollution Index (HPI)
Bhumika Pathak, Rajeev Upadhyay, Shahditta Bakshi, Harish Bisht and Bahadur Singh Kotlia*

In the last few decades, the health of Nainital Lake in the Nainital town (Uttarakhand) has degraded severely due to anthropogenic activity and there is no regular monitoring of the lake in terms of the quality index. We made an attempt to understand the hydrochemical facies and Water Quality Index (WQI) of the lake and nearby springs. The water quality parameters, selected for computation of the WQI were mainly pH, Total Dissolved Solids (TDS), Electrical conductivity (EC), major cations, e.g., Na+, K+, Mg2+, Ca2+, major anions, e.g., F-, Cl-, Br, SO42-, NO3, PO4, alkalinity and heavy metals (Pb, Ni, Mn, Fe, Cu, Cr, Co, Cd, Zn) from eight different locations, four of them from Nainital Lake water and remaining four from nearby springs. This is the first ever study carried out using WQI and HPI indices water and surrounding springs. Additionally, we have also measured Pb, Ni, Mn, Fe, Cu, Cr, Co, Cd and Zn using the Atomic Absorption Spectrometer (AAS) to compute Heavy Metal Pollution Index (HPI). Here, we present two frequently used water quality indices rating scales, i.e., Ramkrishnaiah et al. (2009) and Yadav et al. (2010). The calculated index of the water samples was compared with the standard values of the World Health Organization (2011) and BIS (Bureau of Indian Standard, 1999). Our results indicate that the lake water is highly polluted and is not suitable for drinking without proper purification. This is an upsetting state of affair and the main concern is whether the lake water is properly purified before it is used by about 50,000 residents living around the lake.

Keywords: Nainital Lake; Physical and chemical parameters; Water Quality Index(WQI); Heavy Metal Pollution Index (HPI)