Madhuri Kumari

Clustering Data and Incorporating Topographical Variables for Improving Spatial Interpolation of Rainfall in Mountainous Region

This study was an attempt to quantify the improvement in the accuracy of rainfall interpolation in the mountainous terrain by clustering of rainfall data at the data preparation stage and incorporating topographical variables at interpolation stage. The univariate kriging techniques, ordinary kriging (OK), simple kriging and universal kriging (UK) were compared with multivariate kriging method of ordinary cokriging (OCK). The elevation, slope and terrain ruggedness index (TRI) computed from digital elevation model were incorporated as explanatory variable in OCK. These algorithms were applied to the normal annual and seasonal rainfall data points located in Central Himalayas of Uttarakhand region. The study area was divided into two different zones of lowland and upland based on the elevation variability. This zonation was then used as a basis for clustering the rainfall data. The performance of the interpolation techniques was assessed for subdivided regions and compared with the results obtained for complete region. The evaluation was based on absolute error metrics of root mean square error (RMSE) in combination with RMSE-observations standard deviation ratio. The absolute percentage error (APE) statistics was calculated for every observation points and then the percentage of data for with APE ≤ 30% (APE30) was analyzed. It was observed that performance efficiency of the interpolation methods improves by 5-20% if the rainfall data is clustered based on homogeneity of terrain elevation as against considering the complete set of data. In complex terrain, the inclusion of topographical variables improves the cokriging based rainfall prediction if it is correlated with rainfall.

Comparison of Spatial Interpolation Methods for Mapping Rainfall in Indian Himalayas of Uttarakhand Region

Reliable estimation of rainfall distribution in mountainous regions poses a great challenge not only due to complex relationships between irregular topography and precipitation, but also due to non-availability of abundant rainfall measurement points. This study presents a comparison of univariate and multivariate methods for spatial interpolation of rainfall in complex terrain of Indian Himalayas in Uttarakhand region. To understand the role of topography in explaining the spatial variability of rainfall, elevation and slope calculated from DEM are incorporated as covariables in multivariate interpolation methods. Further, the study area is divided into three different regions based on variation in the elevation of topography and the performance of different spatial interpolation methods is analyzed for subdivided regions. The normal annual rainfall data of 80 rain gauge stations spread over 53,484 km2 is used to generate rainfall map using different interpolation methods. Cross validation is used to compare the prediction performances of the three multivariate geostatistical interpolation algorithms: simple kriging with varying local means (SKlm), ordinary cokriging (OCK), regression kriging (RK) and two univariate techniques: inverse distance weighted (IDW) and ordinary kriging (OK). The inclusion of elevation or slope as auxiliary variables improves the prediction of rainfall in mountainous region. SKlm performs better than OCK in all the cases. Residual kriging outperforms SKlm in Shivalik and Lesser Himalayas region where the correlation between rainfall and elevation is high (rshivalik = 0.79, rlesserhimalayas = 0.5). Also, OCK proves to be a better choice than OK only when the correlation between the rainfall and secondary variable (elevation or slope in this case) is good. When the data of Shivalik region (r=0.79) is considered, the RMSE of OCK is 363 and that of OK is 368. The prediction using OK and OCK yields similar result when the correlation between rainfall and elevation is moderate (r < 0.4). For all the cases, residual kriging outperforms OCK.

Integrated Water Hyacinth Control and Waste Management Plan: A Case of Futala Lake, Nagpur

Water hyacinth belongs to family Pontederiaceae and is a very remarkable and rapidly growing angiospermic plant, generally found in the freshwater bodies. Cost-effective and efficient control of water hyacinth growth and managing its resources is a challenge in most places where the problem has occurred. The present study identifies the effluents from upstream of surrounding area, immersion of idols of Gods during festivals and dumping of domestic garbage as the principal reasons for the growth of water hyacinth in Futala Lake, Nagpur, and proposes an integrated management plan to control the water hyacinth growth and eliminate the municipal solid waste being dumped in the lake at its source. Various studies have determined that besides having pernicious and inimical characteristics, water hyacinth is a remarkable source of biomass and hence makes good organic compost. The study compares the effectiveness of the mechanical, environmental, chemical and biological water hyacinth control methods in conjunction with other waste-to-compost and waste-to-energy technologies in terms of volume reduction, ease of operations, restrictions and conservations on type of waste processing, quality of compost, odour control, ease of organizing human resources, financial feasibility and uses the technology-specific emission factors in conjunction with the Intergovernmental Panel on Climate Change methodologies to determine the annual greenhouse gas (CO2 eq.) emissions from them. The proposed integrated plan uses the inferences obtained from comparing the technical, financial and operational feasibility of applying different water hyacinth control methods in Futala Lake to make one integrated water hyacinth control and management plan and explains the stepwise procedure to eliminate the water hyacinth problem and control the wild dumps of municipal solid wastes near the lake by using waste-to-compost machines working on the principle of thermophilic decomposition. Thus, with respect to the analysis of the efficiency and effectiveness of the proposed management and control plan for Futala Lake, the study proposes that similar plans could be used to check the growth of water hyacinth in any freshwater body.