Water Balance Simulation Model Research Articles

Rainwater harvesting in Greater Sydney: Water savings, reliability and economic benefits

Due to greater environmental awareness and mandatory water restrictions in many Australian cities, rainwater tanks have become popular in recent years. This paper investigates the water savings potential of rainwater tanks fitted in detached houses at 10 different locations in Greater Sydney, Australia. A water balance simulation model on daily time scale is developed and water savings, reliability and financial viability are examined for three different tank sizes, 2kL, 3kL and 5kL. It is found that the average annual water savings from rainwater tanks are strongly correlated with average annual rainfall. It is also found that the benefit cost ratios for the rainwater tanks are smaller than 1.00 without government rebate. It is noted that a 5kL tank is preferable to 2kL and 3kL tanks and rainwater tanks should be connected to toilet, laundry and outdoor irrigation to achieve the best financial outcome for the home owners. The results from this study suggest that government authorities in Sydney should maintain or possibly increase the rebate for rainwater tanks to enhance its acceptance.

Estimation of flow in ungauged catchments by coupling a hydrological model and neural networks: case study

The prediction of hydrological variables for ungauged basins is still a big challenge. Regionalization is the most widely used method to date, which relates parameters of watershed models to catchment characteristics. Relating catchment characteristics to watershed model parameters is too difficult for distributed hydrological models, due to the heterogeneous nature of catchments. A regional model was proposed by coupling a Kohonen neural network (KNN) and distributed Water Balance Simulation Model (WaSiM-ETH) to estimate flow in ungauged basin. KNN was used to delineate a hydrological homogeneous group based on predefined physical characteristics of catchments and WaSiM-ETH was applied to generate daily stream flow. Twenty-six subcatchments of the Blue Nile River basin, Ethiopia, were grouped into five hydrological homogenous groups, each with its own full set of optimized WaSiM-ETH parameters. In the regional model, the KNN assigned the ungauged catchment into one of the five hydrological homogenous groups. The whole set of optimized WaSiM parameters from the homogeneous group (which the ungauged river belongs to) were transferred to the ungauged river and WaSiM-ETH was used to compute the flow for this ungauged river. The regional model generally overestimated the low flow. In general, the results for validation subcatchments showed the regional model is satisfactory in transferring information from data-rich to data-poor catchments.

Field-scale spatial variability of saturated hydraulic conductivity on a recently constructed artificial ecosystem

Saturated hydraulic conductivity ( K s) influences water storage and movement, and is a key parameter of water and solute transport models. Systematic field evaluation of K s and its spatial variability for recently constructed artificial ecosystems is still lacking. The objectives of the present study were; (1) to determine saturated hydraulic conductivity of an artificial ecosystem using field methods (Philip–Dunne, and Guelph permeameters), and compare their results to the constant-head laboratory method; (2) to evaluate the spatial variability of K s using univariate and geostatistical analyses, and (3) to evaluate the ability of five pedotransfer functions to predict K s. The results showed that K s varied significantly (p < 0.05) among methods, probably reflecting differences in scales of measurement, flow geometry, assumptions in computation routines and inherent disturbances during sampling. Mean K s values were very high for all methods (38.6–77.9 m day − 1 ), exceeding values for natural sandy soils by several orders of magnitude. The high K s values and low coefficients of variation (26–44%) were comparable to that of well-sorted unconsolidated marine sands. Geostatistical analysis revealed a spatial structure in surface K s data described by a spherical model with a correlation range of 8 m. The resulting kriged map of surface K s showed alternating bands of high and low values, consistent with surface structures created by wheel tracks of construction equipment. Vertical K s was also spatially structured, with a short correlation range of 40 cm, presumably indicative of layering caused by post-construction mobilization and deposition of fine particles. K s was linearly and negatively correlated with dry soil bulk density (ρ b) (r 2 = 0.73), and to a lesser extent silt plus clay percentage ( Si + C) (r 2 = 0.21). Combining both ρ b and Si + C significantly (p < 0.05) improved the relationship and gave the best predictor of K s (r 2 = 0.76). However, evaluation of five PTFs developed for natural soils showed that they all underestimated K s by an order of magnitude, suggesting that application of water balance simulation models based on such PTFs to the present study site may constitute a bias in model outputs. Overall, the study demonstrated the influence of material handling, construction procedures and post-construction processes on the magnitude and spatial variability of K s on a recently constructed artificial ecosystem. These unique hydraulic properties may have profound impacts on soil moisture storage, plant water relations and water balance fluxes on artificial ecosystems, particularly where such landforms are intended to restore pre-disturbance ecological and hydrological functions.

Application of WaSiM-ETH model to Northern German lowland catchments: model performance in relation to catchment characteristics and sensitivity to land use change

Abstract. The hydrological catchment model WaSiM-ETH (Water Balance Simulation Model) is a spatially distributed, process- and grid-based hydrological catchment model which was primarily developed to simulate the water balance of mountainous catchments. In this study, the ability of WaSiM-ETH was tested to describe the hydrological processes of lowland catchments. In addition, the resulting model performance was related to subcatchment characteristics and the model's sensitivity to possible future land use change. The prediction of the hydrological effects of land use change is a major challenge in contemporary hydrological model applications. The study revealed that WaSiM-ETH is a suitable tool for the simulation of the hydrological behaviour of lowland catchments. However, for a few subcatchments model validation failed. Analysing the correlation between model performance and physiographic catchment characteristics revealed that WaSiM-ETH performs better in sloped catchments compared to plane ones. Modelling results were also better in heterogeneous catchments with respect to soils and vegetation compared to homogenous ones. However, the hydrological reaction to land use change scenarios was similar in all investigated catchments.

Grope in the Dark – Hydrological modelling of the artificial Chicken Creek catchment without validation possibilities

Environmental modelling is often reduced to a calibration–validation exercise in which a thorough understanding of the processes involved is less important than sophisticated parameter estimation tools. A problem occurs when no data are available for calibration and validation. To compare the ability of different models and modellers to describe the hydrological behaviour of ungauged catchments, a model comparison was initiated by Transregional Collaboration Research Centre 38 (SFB/TRR 38). The comparison was conducted in several consecutive stages, in which knowledge of the investigated artificial catchment of approximately 6 ha was enhanced stepwise. For modelling purposes, all basic input data were given, but neither discharge nor soil moisture measurements were provided. This hard information was supplemented stepwise by soft (qualitative) information mostly obtained by a field inspection after the first modelling stage. In this study, the process-based distributed Water balance Simulation Model (WaSiM-ETH) was applied. An initial perceptual model was developed without site-specific knowledge. Significant modifications to the perceptual model were conducted using the available soft information. These modifications resulted in more reliable water fluxes. The main changes, such as the importance of a sealed topsoil layer, vegetation development, initial conditions, and the effects of a small pond on discharge behaviour, were related to process understanding. Although hard information on the water balance was still missing, the qualitative behaviour of the model seemed to be realistic. This underlines the importance of soft information for successful modelling, which is especially important if ungauged catchments are to be investigated.

Simulated impact of past and possible future land use changes on the hydrological response of the Northern German lowland ‘Hunte’ catchment

Summary Land use is a key factor controlling the hydrological behaviour of catchments. Changing land use therefore can have an important influence on the local hydrological cycle. Validated and process-based hydrological models are suitable tools to quantify the impact of a change in land use on the hydrological processes. In this study, the physically based catchment model WaSiM-ETH (Water Balance Simulation Model) was applied to a mesoscale lowland catchment in northern Germany (Hunte river, 2141 km2 at gauge Oldenburg). Model calibration and validation showed that WaSiM-ETH well represented the discharge of the main Hunte river while the discharge dynamics of a few lowland tributaries whose catchments are characterised by peaty soils and intense artificial drainage could not be represented. The purpose of this study was twofold; on the one hand to analyse the sensitivity of WaSiM-ETH to changes in land use observed in the decade 1990–2000, and on the other hand to quantify the impact of land use change projected for the future in terms of land use scenarios available to the public. The results showed that WaSiM-ETH is hardly sensitive to the slight changes observed in the last decade of the 20th century. By contrast, water flows simulated by WaSiM-ETH are clearly impacted by agricultural land use scenarios which were developed based on IPCC scenarios. However, the results also show that it is not sufficient to focus on agricultural land use, only. The proposed reduction of agricultural land leaves open the final land cover after land use change, e.g., forest or urban areas. This study demonstrated that WaSiM-ETH was more sensitive to the choice of the final land cover than to the difference in the scenarios (e.g., A1F1 versus B1). Therefore, we recommend to precisely define change in agricultural land use as well as the final land cover in order to estimate the realistic impact of land use change on hydrological behaviour.

Climate sensitivity of soil water regime of different Hungarian Chernozem soil subtypes

In this study the possible effects of two predicted climate change scenarios on soil water regime of Hungarian Calcic Chernozem soils has been investigated. Soil profiles classified as Calcic Chernozem — in total 49 — were selected from the MARTHA soil physical database that incorporates soil data at national scale. These profiles were subdivided into three groups (sandy loam, loam and clayey loam) in accordance with their mechanical composition. Soil water retention curves were scaled separately for each of the three textural groups, using similar media scaling in order to represent the variability of soil hydrophysical data with one parameter, the scaling factor (SF). Reference soil profiles were chosen according to the cumulative distribution function of the scaling factor, six for each textural group. Daily downscaled meteorological data from A2 and B2 climate scenarios of the Hadley Centre (2070–2100) and data from a reference period (RF, 1961–1990) were used in this study to characterize different climatic situations. Nine representative years were selected in case of all the three scenarios, using the cumulative probability function of the annual precipitation sum. Scenario analyses were performed, validating the SWAP soil water balance simulation model for the 18 reference soil profiles and 27 representative years in order to evaluate the expected changes in soil water regime under different from the present (RF) climatic conditions (A2 and B2 scenarios). Our results show that the scaling factor could be used as a climate sensitivity indicator of soil water regime. The large climate sensitivity of the majority of Chernozem soil subtypes water regime has been proven.

Water balance simulation model for optimal sizing of on-farm reservoir in rainfed farming system

The on-farm reservoir (OFR) is used to harvest the surplus water from the diked crop field and recycle the stored water as supplemental irrigation to rice in monsoon (rainy) and non-rice (dry) crops in winter season under rainfed farming system. A user-friendly software, using Visual Basic 6.0 program, is developed to find out the optimal size of the OFR in terms of percentage of field area (here in called as OFR sizes throughout the manuscript) by simulating the water balance model parameters of the crop field and the OFR. The software is meant for all the concerned including the engineers, planners and farming community for any monsoon influenced cropping area, which uses rainfed agriculture. The menu driven system is flexible enough to simulate the OFR sizes for various combinations of the OFR geometry, field sizes, and the cropping systems. The user has to specify the crops to be grown in the fields, irrigation management practices of the crops, types of OFR (lined or unlined), side slope, depth of OFR, and field sizes. Evapotranspiration sub-model is embedded with the main model to compute the ET from the meteorological data. As model application, the developed model is used to simulate the OFR sizes for the rice–mustard and rice–groundnut cropping systems using the experimental observed and meteorological data of the study area located at Indian Institute of Technology, Kharagpur in eastern India. The water balance model parameters of the crop field are validated with 2 years of observed data from the experimental field of above mentioned study area. The study reveals that rice–groundnut cropping system requires higher OFR sizes than rice–mustard cropping systems. Moreover, it is observed that as the field areas increase, the OFR sizes for each cropping systems is found to decrease.

A Chernozem soil water regime response to predicted climate change scenarios

Climate, hydrology and vegetation are closely linked at local, regional and global scales. The recent land use and plant production systems are adapted to the present climatic conditions. Thus, studies on the influence of possible climate change scenarios on the water and heat regimes of the soil-plant-atmosphere system are important in order to work out plant production strategies, adjusted to changed conditions. In this study the effect of two possible climate change scenarios on the soil water regime of a Chernozem soil was estimated for a Hungarian site. Soil water content dynamics simulated for different conventional and soil conserving soil tillage systems were evaluated, using the SWAP soil water balance simulation model. The combined effect of different soil tillage systems and climate scenarios was analysed. Climate scenarios were represented through the cumulative probability function of the annual precipitation sum. The SWAP model was calibrated against the measured in the representative soil profiles soil water content data. The site- and soil-specific parameters were set and kept constant during the scenario studies. According to the simulation results, increase in the average growing season temperature showed increase in climate induced soil drought sensitivity. The evaluated soil water content dynamics indicated more variable and less predictable soil water regime compared to the present climate. It was found that appropriate soil tillage systems that are combined with mulching and ensure soil loosening could reliably decrease water losses from the soil. From this aspect cultivator treatment created the most favourable for the plants soil conditions. It was concluded that soil conserving soil management systems, adapted to local conditions could contribute to soil moisture conservation and could increase the amount of plant available water under changing climatic conditions.

Comparison of Field Performance of Multiple Soil Moisture Sensors in a Semi‐Arid Rangeland1

Abstract: Automated electronic soil moisture sensors, such as time domain reflectometry (TDR) and capacitance probes are being used extensively to monitor and measure soil moisture in a variety of scientific and land management applications. These sensors are often used for a wide range of soil moisture applications such as drought forage prediction or validation of large‐scale remote sensing instruments. The convergence of three different research projects facilitated the evaluation and comparison of three commercially available electronic soil moisture probes under field application conditions. The sensors are all installed in shallow soil profiles in a well instrumented small semi‐arid shrub covered subwatershed in Southeastern Arizona. The sensors use either a TDR or a capacitance technique; both of which indirectly measure the soil dielectric constant to determine the soil moisture content. Sensors are evaluated over a range of conditions during three seasons comparing responses to natural wetting and drying sequences and using water balance and infiltration simulation models. Each of the sensors responded to the majority of precipitation events; however, they varied greatly in response time and magnitude from each other. Measured profile soil moisture storage compared better to water balance estimates when soil moisture in deeper layers was accounted for in the calculations. No distinct or consistent trend was detected when comparing the responses from the sensors or the infiltration model to individual precipitation events. The results underscore the need to understand how the sensors respond under field application and recognize the limitations of soil moisture sensors and the factors that can affect their accuracy in predicting soil moisture in situ.

A mathematical model for simulating water balances in cropped sandy soil with conventional flood irrigation applied

In this paper, a model that integrates various complex model components for the purposes of water balance modeling throughout crop development in arid inland region under the conventional flood irrigation practiced is presented. These components are modules for calculating dynamic soil water content based Richard's equation, potential and actual evapotranspiration, and crop root water uptake. Soil water content in the active root zone and soil evaporation simulation obtained from the model were test using field data in 2003. The low values of MARE and high values of R 2 and PE in the active root zone of soil profile as well as daily soil evaporation indicated that the soil water balance simulation model presented in the paper can be used with reliable accuracy to simulate the components of water balance in cropped sandy soil under the conventional flood irrigation condition in arid inland regions. The model simulation on components of water balance using observed field data in 2004 indicated that large quantities – about 43% of irrigation water (amounting to 840 mm) – were consumed by deep percolation, only small (less than 41%) proportions of irrigation water used by the plants for transpiration. The current irrigation scheme is characterized by the unreasonable agricultural water management with the waste of water in the irrigational system in this region. The impact of irrigation scheduling on water balance presented in this paper showed that the reasonable irrigation scheme with more frequent irrigation and less amounts is more suitable for the irrigation of spring wheat in Heihe River basin, northwest China. Therefore, to establish a decision-making system for agricultural irrigation scheme and to utilize the limited water resources in this region have become an urgent problem that needs to be solved.

Flow analysis with WaSiM-ETH – model parameter sensitivity at different scales

Abstract. WaSiM-ETH (Gurtz et al., 2001), a widely used water balance simulation model, is tested for its suitability to serve for flow analysis in the context of rainfall runoff modelling and flood forecasting. In this paper, special focus is on the resolution of the process domain in space as well as in time. We try to couple model runs with different calculation time steps in order to reduce the effort arising from calculating the whole flow hydrograph at the hourly time step. We aim at modelling on the daily time step for water balance purposes, switching to the hourly time step whenever high-resolution information is necessary (flood forecasting). WaSiM-ETH is used at different grid resolutions, thus we try to become clear about being able to transfer the model in spatial resolution. We further use two different approaches for the overland flow time calculation within the sub-basins of the test watershed to gain insights about the process dynamics portrayed by the model. Our findings indicate that the model is very sensitive to time and space resolution and cannot be transferred across scales without recalibration.

Model based distributed water balance monitoring of the White Volta catchment in West Africa through coupled meteorological-hydrological simulations

Abstract. Sustainable water management requires the quantification of the spatial and temporal changes of water balance variables. Fully distributed hydrological simulations of these variables are especially in regions with weak infrastructure challenging, because the required meteorological input data are often not available in a sufficient spatial and temporal resolution. One possibility to deal with this limitation is to provide the required input data with a meteorological model. This combination results in a one way meteorological-hydrological coupling system. Within the framework of the GLOWA-Volta project it is investigated to what extent meteorological models are able to provide the required meteorological fields with sufficient accuracy for the hydrological modeling. For this study the mesoscale meteorological model MM5 and the fully distributed water balance simulation model WaSiM-ETH were first adapted and validated separately. The research area is the White Volta catchment in the semi-arid to sub-humid climate zone in West Africa. The meteorological simulations tend toward overestimating measured precipitation sums. The coupled meteorological-hydrological runoff simulations show similar model performances as the simulations driven by observations indicating the potential of this system for a contemporary estimation of the terrestrial water balance.

OSIRI: A simple decision-making tool for monitoring irrigation of small farms in heterogeneous environments

A new decision-making software tool for sprinkler or drip irrigation scheduling and monitoring, was developed at the request of small scale sugarcane ( Saccharum spp.) farmers in Reunion Island (France) facing variable climate and soil conditions. Based on a simple water balance simulation model coupled with a comprehensive set of decisions rules, OSIRI was designed to provide farmers with targeted advices on discrete units of irrigation and for simulating scenarios of irrigation systems to optimize their performance. An optional procedure of direct adjustment by farmers and a system of controlled irrigation rationing are proposed. To meet the producer needs, the number of input parameters is adapted to the rather limited data availability, and the recommendation sheet is user-friendly oriented. Field data confirmed that OSIRI simulates very reasonably well actual evapotranspiration and drainage below the sugarcane root zone. Also, OSIRI allowed to save about 30% of irrigation delivery on a 140-day period as compared to the currently used crop water requirement method (respectively, 165 and 240 mm of water), without significant decrease in yield (respectively, 102 and 101 T ha −1).

Fluxes through the bottom boundary of the root zone in silty soils: Parametric approaches to estimate groundwater contribution and percolation

The paper revises empirical and semi-empirical approaches used with water balance models to estimate the capillary rise from a water table and the deep percolation through the bottom of the root zone and describes simple parametric functions to be used with the water balance simulation model ISAREG. The relationships between upward flux, water table depth, soil water storage and crop evapotranspiration were developed from analysing results of simulations with the deterministic flux model WAVE. Field experiments with wheat and maize were used to calibrate this model and to validate the new approaches with the ISAREG water balance model. The application refers to a silty soil in the North China Plain, which hydraulic properties were studied through in situ and laboratory measurements. Observations included the soil water content, the soil water potential and the water table dynamics. The validation of the approach was performed by comparing ISAREG simulations with observed soil water contents during periods when upward or downward fluxes were observed; the resulting regression coefficient is close to 1.0 and the average relative error of estimate, ARE, is 1.38%. The cumulated upward fluxes computed with ISAREG and WAVE for a 3-month period are similar, respectively, 27 and 31 mm. Simulations with ISAREG were performed for other soils to analyse the impacts on upward fluxes when the model parameters are changed to be applied to different soils. Results for the validation of the percolation approach when comparing simulated and observed soil water content data for a maize crop season produced a coefficient of regression also close to 1.0 and an ARE of 2.18%. It could be concluded that the proposed simulation approaches for the groundwater contribution and percolation produce accurate predictions of the daily soil water content in presence of a water table for irrigation scheduling purposes.

Return‐flow assessment for irrigation command in the Palleru river basin using SWAT model

AbstractDue to the ever‐increasing demand for water resources, the pressure on their judicious utilization is also increasing. Besides being precious, water is also a very complex commodity. The dynamic nature of weather as well as the spatial variability of landmass contribute to the dynamic behaviour of the response of the watersheds to the natural and artificial inputs of water. This requirement has led to the formulation of continuous, distributed parameter, water balance simulation models capable of providing insight into the distribution and utilization of water in a watershed. Since they mimic the natural processes prevalent in the area, they are capable of providing many answers that are normally not easily available otherwise. In the present paper one such situation has been tackled using the SWAT (Soil and Water Assessment Tool) model. The target question was to assess the return flow on account of introducing canal irrigation in a basin (Palleru river basin in the southern state of Andhra Pradesh, India). Since the return flow is dependent on many aspects such as soil characteristics, method of irrigation, etc., it is not appropriate to put a rule‐of‐thumb value on such quantities. Through modelling, the return flow has been assessed and validated. The temporal variation of such return flows has also been captured. The virgin flows from the basin, before the manmade changes in construction of reservoir and importing water for irrigation were introduced, were also computed as per the requirement of the department. In fact this has been an exercise in demonstrating the usefulness of creating such a base framework capable of helping water managers in planning and management of this very vital resource. Copyright © 2005 John Wiley &amp; Sons, Ltd.

Field test of a soil water balance simulation model

A simple soil water balance model is used to simulate the soil water content in the active root zone of mustard crop ( Brassica juncea) as well as is tested with field experimental data of 2 years (1998 and 1999) under rain-fed (no irrigation) and irrigated conditions. The model used includes physical process like infiltration from rainfall or irrigation, redistribution in soil water zone, plant water uptake in the form of actual evapotranspiration and percolation out of the soil reservoir. In addition, the model considers dynamics of crop root growth model that affect the plant water uptake and hence the soil water in the unsaturated zone. The model satisfactorily simulates the soil water content in the active root zone of the crop on daily basis. Values of the mean absolute relative error (MARE) index between the observed and simulated soil water content of the rain-fed mustard in 1998 and 1999 are found to be 0.046 and 0.058, respectively, whereas for irrigated mustard, it is 0.051 in 1999. Prediction efficiency (PE) index is found to be 0.98, 0.97 and 0.97 for rain-fed mustard of 1998 and 1999 and irrigated mustard of 1999, respectively. Since the MARE index is low and PE index is high for both rain-fed and irrigated mustard, the model can be used to simulate the soil water content in the active root zone of the crop.

Water Budget Approach to Quantify Corn Grain Yields Under Variable Rooting Depths

This study investigated the relationships between corn (Zea mays L.) grain yield and weather over a range of soil rooting depths with and without irrigation. The purpose was to test if variability of corn grain yield over a range of soil rooting depths could be reduced if water is supplied via irrigation. An additional goal was to test a simple water balance simulation model which calculates a seasonal moisture stress index based on relative evapotranspiration deficits. Such a water budget model could be used to estimate variations in corn grain yields as a function of spatial differences in soil depth and available water holding capacity in site specific agriculture. Corn grain yields were measured over a 3‐yr period from 70 plots at the Cornell University Robert Musgrave Research Farm at Aurora, NY, USA. Soil depths ranged from 0.2 to 1 m. During one year of the study, paired irrigated and non irrigated plots were placed at locations that had varying soil rooting depths. Irrigation resulted in significant increases in grain yield with the greatest response occurring on the soils with less than 0.5 m of rooting depth. Yields under irrigation were similar at all soil depths suggesting that, as soil depth decreased on these soils, water was the major limiting factor. The water budget model gave satisfactory estimates of grain yields as a function of soil depth and available water capacity and appears to be a useful tool to estimate corn grain yield as a function of soil depth and available water. The estimated potential yields can be used as a guide for site specific soil management given variations in available water holding capacity that affect potential soil productivity.

Assessment of three monthly rainfall-runoff models for estimating the water resource yield of semiarid catchments in Namibia

Three monthly rainfall-runoff models have been applied to semiarid catchments within Namibia under the Southern African FRIEND (Flow Regimes from International Experimental and Network Data) programme. These are the Namrom model, developed specifically for Namibia, and two versions of the Pitman model, developed in South Africa and applied throughout the southern African region. The models were all calibrated on about 20 years of observed flow data and the calibrated parameters used to generate 68 years of simulated inflows to reservoirs located at the catchment outlets. A reservoir water balance simulation model was used with the three inflow series to assess the differences resulting from the application of the three models, with respect to estimates of the reliable yield. The calibration results for the three models were not very different and suggested that the yield estimates would be similar. However, the results based on the 68-year inflow records produced greater differences in yield which could have serious implications for the planning and management of water supply schemes.

Tree clearing and dryland salinity hazard in the Upper Burdekin Catchment of North Queensland

This paper provides experimental data on the effect of tree clearing, introduction of perennial Stylosanthes based pastures, and the use of native grasses on the water balance of a red earth soil in the Upper Burdekin Catchment near Charters Towers. The water balance simulation models SWIM and PERFECT are used to extend the results and estimate deep drainage for this and other soils in this tropical environment. The analysis illustrates that the soil/climate interaction in the wet/dry tropics has a similarity with the winter-dominant rainfall zone where vegetation change can substantially increase deep drainage beyond the root-zone. Salt distribution in the soil/landscapes of the Upper Burdekin suggests that there is a salinity hazard, should a significant shift in the water balance occur as a result of tree clearing. Therefore, in the Upper Burdekin Catchment of North Queensland, indiscriminate tree clearing is a hazardous form of land management and should only proceed after the risks of dryland salinity have been evaluated and shown to be negligible.