Sina Alaghmand

Comparing three approaches of evapotranspiration estimation in mixed urban vegetation: Field-based, remote sensing-based and observational-based methods

Despite being the driest inhabited continent, Australia has one of the highest per capita water consumptions in the world. In addition, instead of having fit-for-purpose water supplies (using different qualities of water for different applications), highly treated drinking water is used for nearly all of Australia’s urban water supply needs, including landscape irrigation. The water requirement of urban landscapes, particularly urban parklands, is of growing concern. The estimation of evapotranspiration (ET) and subsequently plant water requirements in urban vegetation needs to consider the heterogeneity of plants, soils, water, and climate characteristics. This research contributes to a broader effort to establish sustainable irrigation practices within the Adelaide Parklands in Adelaide, South Australia. In this paper, two practical ET estimation approaches are compared to a detailed Soil Water Balance (SWB) analysis over a one year period. One approach is the Water Use Classification of Landscape Plants (WUCOLS) method, which is based on expert opinion on the water needs of different classes of landscape plants. The other is a remote sensing approach based on the Enhanced Vegetation Index (EVI) from Moderate Resolution Imaging Spectroradiometer (MODIS) sensors on the Terra satellite. Both methods require knowledge of reference ET calculated from meteorological data. The SWB determined that plants consumed 1084 mm·yr−1 of water in ET with an additional 16% lost to drainage past the root zone, an amount sufficient to keep salts from accumulating in the root zone. ET by MODIS EVI was 1088 mm·yr−1, very close to the SWB estimate, while WUCOLS estimated the total water requirement at only 802 mm·yr−1, 26% lower than the SWB estimate and 37% lower than the amount actually added including the drainage fraction. Individual monthly ET by MODIS was not accurate, but these errors were cancelled out to give good agreement on an annual time step. We conclude that the MODIS EVI method can provide accurate estimates of urban water requirements in mixed landscapes large enough to be sampled by MODIS imagery with 250-m resolution such as parklands and golf courses.

A review of the numerical modelling of salt mobilization from groundwater-surface water interactions

Salinization of land and water is a significant challenge in most continents and particularly in arid and semi-arid regions. The need to accurately forecast surface and groundwater interactions has promoted the use of physically-based numerical modelling approaches in many studies. In this regard, two issues can be considered as the main research challenges. First, in contrast with surface water, there is generally less observed level and salinity data available for groundwater systems. These data are critical in the validation and verification of numerical models. The second challenge is to develop an integrated surface-groundwater numerical model that is capable of salt mobilization modelling but which can be validated and verified against accurate observed data. This paper reviews the current state of understanding of groundwater and surface water interactions with particular respect to the numerical modelling of salt mobilization. 3D physically-based fully coupled surface-subsurface numerical model with the capability of modelling density-dependent, saturated-unsaturated solute transport is an ideal tool for groundwater-surface water interaction studies. It is concluded that there is a clear need to develop modelling capabilities for the movement of salt to, from, and within wetlands to provide temporal predictions of wetland salinity which can be used to assess ecosystem outcomes.

Comparison between capabilities of HEC-RAS and MIKE11 hydraulic models in river flood risk modelling (a case study of Sungai Kayu Ara River basin, Malaysia)

River flood risk map prediction is a combination of hydrological modelling, hydraulic modelling, river flood visualisation and river flood risk mapping. Two hydraulic models were applied in this research regarding their capabilities in river flood risk studies. These are MIKE11 developed by Danish Hydraulic Institute (DHI) and HEC-RAS4.0 by US Army Corps of Engineers. These two hydraulic models are compared in four aspects including credibility, available outcomes, usability of the models and the availability. Sungai Kayu Ara River basin is the case study in this research which is located in Kuala Lumpur, Malaysia. The results of the models were compared against observed water level at the outlet of the river basin. The results of this research show that HEC-RAS has more capabilities for river flood risk mapping in comparison with MIKE11 in this case study.

Prediction of Surface Flow by Forcing of Climate Forecast System Reanalysis Data

Meteorological data are key variables for hydrologists to simulate the rainfall-runoff process using hydrological models. The collection of meteorological variables is sophisticated, especially in arid and semi-arid climates where observed time series are often scarce. Climate Forecast System Reanalysis (CFSR) Data have been used to validate and evaluate hydrological modeling throughout the world. This paper presents a comprehensive application of the Soil and Water Assessment Tool (SWAT) hydrologic simulator, incorporating CFSR daily rainfall-runoff data at the Roodan study site in southern Iran. The developed SWAT model including CFSR data (CFSR model) was calibrated using the Sequential Uncertainty Fitting 2 algorithm (SUFI-2). To validate the model, the calibrated SWAT model (CFSR model) was compared with the observed daily rainfall-runoff data. To have a better assessment, terrestrial meteorological gauge stations were incorporated with the SWAT model (Terrestrial model). Visualization of the simulated flows showed that both CFSR and terrestrial models have satisfactory correlations with the observed data. However, the CFSR model generated better estimates regarding the simulation of low flows (near zero). The results of the uncertainty analysis showed that the CFSR model predicted the validation period more efficiently. This might be related with better prediction of low flows and closer distribution to observed flows. The Nash-Sutcliffe (NS) coefficient provided good- and fair-quality modeling for calibration and validation periods for both models. Overall, it can be concluded that CFSR data might be promising for use in the development of hydrological simulations in arid climates, such as southern Iran, where there are shortages of data and a lack of accessibility to the data.

Impacts of Vegetation Cover on Surface-Groundwater Flows and Solute Interactions in a Semi-Arid Saline Floodplain: A Case Study of the Lower Murray River, Australia

Despite many studies on floodplain vegetation, there is limited quantitative understanding of the role of vegetation in surface water (SW) and groundwater (GW) interactions through processes such as evapotranspiration. Moreover, most of the investigations that have been undertaken on SW-GW interactions consider 1D or 2D model set-ups. In addition, most of the modelling studies in this research area have only included water but not solute transport. This paper presents the results of a study on the potential impacts of vegetation cover on the interaction of a river and a saline semi-arid floodplain aquifer using a 3D physically-based fully integrated numerical model. In this regard the following three scenarios were defined: current vegetation cover (calibration model), deep-rooted vegetation cover and shallow-rooted vegetation cover. Clark’s Floodplain, located on the Lower Murray River in South Australia was selected as the study site. The results show that deep-rooted vegetation cover may maintain relatively deeper groundwater levels and a less saline floodplain aquifer. Also, it is shown that in the shallow-rooted scenario, most of the ET component belongs to the evaporation process due to shallower groundwater. On the other hand, the deep-rooted model includes groundwater uptake largely via a transpiration process, and consequently keeps the groundwater levels below the evaporation depth. Overall, in semi-arid areas, the vegetation cover type can have significant impacts on the flow and solute interaction dynamics of a river and a floodplain aquifer due to the influence of ET as a dominant hydrological driver.

Local Scour Around Lateral Intakes in 180 Degree Curved Channel

Local scour on hydraulic structures is one of the most significant problems which are always considered by hydraulic engineers. If the local scour depth is estimated less than real one it can lead the hydraulic structure to fail. On the other hand, if this depth is estimated more than real local scour depth, that construction has no economical justification. Lateral intake is one the hydraulic structures which are used for water conveyance for the purpose of domestic, agricultural and industrial use. Since streamlines near the lateral intake are curved and diverted to lateral intake, some vortices are formed and local scour is observed near the lateral intake. Due to the secondary flow in a river bend, the scour develops near the outer bank and sediment moves toward the inner bank from the outer bank of the bend. Therefore the outer bank of the bend is best location for lateral intake. In this study, experiments were conducted on 180 degree curved channel. In order to consider the effect of lateral intake position on the maximum local scour depth, the lateral intake was situated on 90, 115 and 150 degree. The experiments showed that two scour holes, one in the upstream and the other in the downstream edge of lateral intake, are formed near the lateral intake. Moreover it was found that the maximum depth of scour hole occurs on 90° location. Also the length of scour hole in 150° is the longest.