v notch measuring weirv notch sharpe crest weirv shape sharp crested weirv shaped depressionvacummvacuolarvacuolatevacuolationvadoes zonevadosevadose watervalidationvalleyvalley fillvalley springvalley storagevalley trainvalley windvalu elementvalvevan allen radiation beltvan contractionvaporvaporimetervaporizationvapourvapour pressurevapour transportationvariabilityvariablevariancevaried flowvarnish = desert varnishvarvevectofluviometervector mapvector spaceveering of windveering windvegetated channelvegetation covervelocityvelocity area methodvelocity coefficientvelocity distributionvelocity headvelocity head coefficientvelocity metervelocity of approachvelocity of retreat