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Design of meteorological data networks. Dr. Anil Kumar Lohani National Institute of Hydrology, Roorkee India. Hydro-Met Network Design Workshop, April 6-11, 2015 Kolkata. OBJECTIVES OF NETWORK DESIGN. Water resources assessment at basin or sub-basin scale
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Design of meteorological data networks Dr. Anil Kumar Lohani National Institute of Hydrology, Roorkee India Hydro-Met Network Design Workshop, April 6-11, 2015 Kolkata
OBJECTIVES OF NETWORK DESIGN • Water resources assessment at basin or sub-basin scale • Water resources assessment for administrative geographical unit • Water resources project planning including: • Irrigation, • Domestic (domestic use, livestock watering), • Hydroelectric power and other power generation, • Environmental requirements, • Industrial requirements, • Navigation, • Tourism, recreation • Flood management • Assessing impacts of Climate Change on Water Resources
Network review and design.... • Institutional set-up: to ensure co-ordination/integration of data collection networks. • Data need identification: existing and potential future data users are approached to identify their data needs. • Objectives of network: based on outcome of step 2, objectives of required network are determined. • Prioritisation: a priority ranking among objectives is made in case of budget constraints. • Network density: based on objectives, required network density is determined, taking in view correlation structure of variable(s).
Steps for network review and design.... • Review existing network: existing network density versus required, available equipment and its adequacy, adequacy of operational procedures and possible improvements. • Sites and equipment selection: if existing network requires expansion. • Cost estimation: costs to construct, operate and maintain existing and new stations. • Cost-effectiveness analysis: cost and effectiveness are compared. Steps 5 to 8 are repeated if budget is insufficient to cover costs. • Implementation: once design is approved, network is implemented. • Network should be reviewed after 3 to 5 years. Above procedure should be repeated.
RAINFALL NETWORK: Measuring Objective • Water resources assessment, projects planning and management • Drinking/ Industrial/ Municipal water supply, Navigation, Recreation Activities • Hydrologic design of structures, • Agriculture Water Management • Irrigation, Rain-fed agriculture • Disaster warning systems, and protection: • Flooding, Drainage, Hydrological forecasting • Ecologically sound water systems: • Ecology and Forestry, Erosion, Discharge of effluents • Hydropower generation • Research Major uses of Rainfall data
RAINFALL NETWORKS • Ultimate aim from RF network is to get reliable estimates of areal RF, and/or long term mean values. • Due to spatial correlation among point RF stations and (near) absence of serial correlation, these objectives will lead to different networks. • Correlation reduces effective number of data. • Due to spatial correlation, data in time are more effective then data in space. • A less dense network operated for a longer period is more cost-effective than a denser network providing the same number of RF data. • A reduction in network density adversely affects quality of individual areal estimates.
Network Design: Measure of Effectiveness • To evaluate an optimal design of monitoring system, a measure is required to quantify its effectiveness. • This measure depends on monitoring objectives and should be related to admissible error in estimating the underlying variable. • This error is a function of sampling locations, frequency and accuracy.
Methods of Network Design • Cv Method • Key Station Network Method • Spatial correlation Method • Entropy Method • WMO Guidelines
NETWORK DENSITY WMO recommendations (2008) for minimum densities of stations (area in km2 per station)
NETWORK DENSITY WMO (2008) recommended minimum densities of river gauging stations (area in km2 per station)
NETWORK DENSITY Prioritisation system • In the first instance, “ideal” network size is determined. • All potential users of data should be consulted. • Each station in “ideal” network should be prioritised.
