analysis of help model application in smi-arid areas, study on tehran test cells

hydrologic evaluation of landfill performance (help) model is one of the most accepted tools to simulate the hydrological attributes of landfills. although some major deviations from real values has been reported about the calculated results for leachate generation by help model but other researchers and/or engineers in practice have used it in some places to estimate amount of leachate produced in the landfills. on the other hand this model is elaborated and mainly used in developed countries with the waste having low moisture content and also in climatic conditions with high precipitation. this research investigated the applicability of the model in arid areas, by construction of two 30m× 50m (effective horizontal length) test cells in kahrizak landfill (longitude=51°, 20', latitude= 35° 27' degrees), and monitoring the real leachate generation from each one. a set of field capacity and saturated water conductivity tests were also performed to determine basic hydrologic properties of municipal waste landfilled. a comparison was made between values calculated by help model and recorded values, shows that a prediction of leachate on annual basis can be done by help model with acceptable accuracy but when the infiltration of water to waste body increases due to leachate production, the model intents to underestimate water storage capacity of the landfill, which lead to deviation of calculated values from real ones.