Daily Water Requirements of Vegetation in the Urban Green Spaces in the City of Panaji, India

From the urban sustainability perspective and from the steps essential for regulating/balancing the microclimate features, creation and maintenance of urban green spaces (UGS) are vital. The UGS include vegetation of any kind in urban areas such as parks, gardens, vertical gardens, trees, hedge plants, and roadside plants. This “urban green infrastructure” is a cost-effective and energy saving means for ensuring sustainable development. The relationship between urban landscape patterns and microclimate needs to be sufficiently understood to make urban living ecologically, economically, and ergonomically justifiable. In this regard, information on diverse patterns of land use intensity or spatial growth is essential to delineate both beneficial and adverse impacts on urban environment. With this background, the present study aimed to address water requirements of UGS plants and trees during the non-rainy months from Panaji city (Koppen classification: Am) situated on the west coast of India which receives over 2750 mm rainfall almost exclusively during June-September period. In the remaining eight months irrigating the plants in the UGS becomes a serious necessity. The methods followed included primary (field survey-based) and secondary (inputs from key-informant survey questionnaires) data collection address water requirement of the UGS vegetation. Monthly evapotranspiration rates (ET0) derived in this study were used for calculating the water requirement of the UGS. The daily water requirements (DWR) in seven gardens of Panaji city were ~ 25 litres/tree, 6.77 litres/m2 hedge plants and 4.57 litres/m2 groundcover (=lawns). The water requirements for the entire UGS in Panaji city were calculated. Using this information, the estimated total daily volume of water required for the entire UGS of 1.86 km2 in Panaji city is 7.10 million litres. The day-night average ET0 being over 8mm, there appears to be an imminent water stress in most UGS of the city in particular during January-May period. The current supply from borewells of 64200 L vis a vis this ET0 based DWR of 184086 L is at a shortage of over 2.88 times far inadequate in meeting the daily demand of hedge plants and lawn/groundcover.