In the urban green space due to the microclimate, plant species diversity, plant density and size of the canopy, especially in dry areas with scarcity of water resources such as Isfahan, it is necessary to determine green space water requirement for irrigation scheduling. The aim of this study was to determine water requirement of four important areas of green space of park Nazhvan and comparison with the volume of water that have been used in the current management. Reference evapotrairation calculated by using meteorological data and FAO-Penman-Monteith method. Water demand of green space were calculated using WUCOLS method. The results showed that the maximum water requirement of green space occurred in June and July, and time and amount of maximum water requirement for different green space in the park Nazhvan was vary. The highest difference in annual water requirements among different green space was 23 percent, between green space of Nasrbridge-Luleh Park and Manibridge-Nasrbridge. The cumulative volume of water demand in spring and summer was 280, 220, 145 and 115 thousand cubic meters for Nasrbridges-Luleh Park, Bishehroghani, Manibridge-Nasrbridges and Mirza Kochakkhan Park, respectively. Whereas, the total volume of applied water for two mention seasons in the last years was 870 thousand cubic meters. Overall, applied water in the Nazhvan was 12.5% more than the net water requirement. However, due to low irrigation efficiency and mismanagement, the branches of trees were exposed to dryness and Nazhvan was faced with a reduction of size of the canopy. Factors such as technical mistake in the design, selection of materials and implementation of pressurized irrigation systems, using traditional irrigation method with low efficiency, and unsuitable irrigation management caused water stress occurred in green space of Nazhvan. Given green space water requirement and the amount of available water in Nazhvan, traditional irrigation method and sprinkler irrigation system are not suitable. However, it is possible to irrigate green space of the Nazhvan without water stress with using a technical and accurate drip irrigation system with good implementation and strict scientific management by using same available water amount. Keywords : Nazhvan parks, water requirements, intercropping, green space ratio, FAO-Penman-Monteith.