Conference Agenda

Floods impact on human survival, economic development and environmental sustainability through loss of life and economic loss as a consequence of the failure of hydraulic structures (e.g. drainage systems, and dams). Estimates of design floods are required for the design of hydraulic structures and to quantify the risk of failure of the structures. Most of the methods currently used for design flood estimation in South Africa were developed in the late 1960s and early 1970s and require updating with more than 40 years of additional data currently available and with new approaches used internationally. In addition, climate change is expected to influence the magnitude and frequency of flooding, and hence this increased variability in flows needs to be accounted for when determining flood risk. Given the above, a National Flood Studies Programme (NFSP) has been initiated to update the methods. This presentation will provide some background to the NFSP and an overview of new developments to date. These new methods have been incorporated in the development of a QGIS-based National Flood Studies Application Tool (NaFSAT), which will support easy and consistent national scale application of design flood estimation methods by practitioners.

Efficient irrigation management is essential to enhance crop productivity and water-use efficiency under increasing climate variability, particularly in controlled agricultural systems. Advances in automated irrigation and soil-based decision tools provide opportunities to optimize water application according to soil hydraulic behavior and crop requirements.

This study evaluated a soil-specific automated irrigation strategy integrating locally calibrated soil moisture sensors with irrigation thresholds derived from soil water retention curves. A greenhouse experiment was conducted using basil (Ocimum basilicum L.) grown in sandy loam and clay soils under three irrigation regimes (deficit, optimal, and excess), defined based on permanent wilting point, field capacity, and a predefined fraction of available water. A total of 60 pots were evaluated with ten replicates per treatment and soil type over two consecutive crop cycles.

Results showed that optimal irrigation increased dry biomass by approximately 31–33% compared to deficit and excess irrigation regimes, indicating improved irrigation performance and more stable soil moisture regulation. Soil type significantly influenced crop response, as sandy loam achieved the highest biomass yield (3.06 units), while clay soil reached 1.55 units.

These findings highlight the potential of soil-specific automated irrigation to improve irrigation scheduling precision and crop productivity in greenhouse production systems.

Water erosion and sediment transport are critical processes contributing to soil degradation in tropical agricultural systems, particularly under steep slopes and high-intensity rainfall events. The objective of this study was to analyze the influence of slope on runoff generation, soil loss, and sediment transport under controlled rainfall simulation conditions, and to evaluate the predictive performance of models commonly used in erosion studies. Laboratory experiments were conducted using runoff plots and a rainfall simulator calibrated to an intensity of 120 mm/h. Four slope conditions were evaluated: 10%, 15%, 20% without conservation practice, and 15% with infiltration trenches as conservation practice, with three replicates per treatment. The same soil material was used in all experiments and was characterized by texture, bulk density, aggregate stability, shear strength, and soil moisture. Hydrological and sediment variables were measured, including runoff volume, discharge, sediment concentration, and soil loss. Observed erosion ranged approximately from 0.5-1.3 kg/m² at 10% slope to 12-16 kg/m² at 20% slope. Statistical analysis showed significant differences among slope treatments (ANOVA, p<0.001). Estimates obtained using the RUSLE, WEPP, and Yalin equation models showed deviations from the experimental values, highlighting the need to validate erosion and sediment transport models under conditions representative of tropical environments.

Surface irrigation performance in sugarcane systems is strongly influenced by soil hydraulic variability, yet quantitative evaluations under temperate production conditions remain limited. This study aimed to assess furrow irrigation performance in commercial sugarcane fields in Uruguay under contrasting soil textures and to evaluate the ability of a hydraulic model to reproduce observed advance and infiltration dynamics. Field experiments were conducted to measure advance and recession times along furrows representative of commercial management. A one-dimensional hydraulic surface irrigation model was calibrated using observed advance data and applied to estimate spatial infiltration patterns and irrigation performance indicators, including application efficiency and distribution uniformity. Marked differences in advance rate and infiltration opportunity time were observed between soil textures, leading to significant variations in infiltrated depth distribution along the furrow. Soil-dependent infiltration behavior directly affected application efficiency and deep percolation losses. The hydraulic model adequately reproduced field advance trajectories, supporting its use as a diagnostic tool for system evaluation. The results demonstrate that soil-specific parameterization is essential for improving furrow irrigation management in sugarcane under temperate conditions. Integrating field measurements with hydraulic modeling provides a robust framework for optimizing operational variables and enhancing water use efficiency in surface-irrigated systems.

Over the last few decades, concern about turfgrass water requirements has increased. Among the objectives, the use of warm-season species, which are more tolerant of deficit irrigation, has been a main strategy. In this paper, we evaluate the effect of deficit irrigation on the presence of spontaneous vegetation on turfgrass surfaces in early spring. Deficit irrigation in the previous season was 100, 75, and 50 % of Et0. Three types of turfgrass were evaluated: Cynodon dactylon x Cynodon transvaalensis ‘Texoma’, Zoysia matrella ‘Zorro’, and a mix of Cynodon dactylon x Cynodon transvaalensis ‘Texoma’ with overseed of Festuca arundinacea and Lolium perenne. The presence of spontaneous vegetation has been evaluated using the Green Leaf Index. The results demonstrated that both irrigation regime and species are significant factors in the presence of spontaneous vegetation (p-values < 0.0001 and 0.0025, respectively). Plots under severe deficit irrigation have significantly more spontaneous vegetation than those under mild or no deficit irrigation. Among species, plots composed of Cynodon dactylon x Cynodon transvaalensis are less affected by spontaneous vegetation. These results indicate that, although overall quality and survival remain stable, early‑spring management requirements increase due to enhanced spontaneous vegetation under deficit irrigation.

Accurate estimation of actual evapotranspiration (ETa) remains a major challenge in tropical irrigated systems due to strong spatial heterogeneity and limited ground-based observations. This study evaluates the METRIC energy balance model in Costa Rica as a critical step toward assessing its spatial transferability and enabling operational ETa monitoring. A three-stage framework was implemented: (1) validation against Eddy Covariance (EC) measurements, (2) assessment of spatial transferability by evaluating the influence of different meteorological stations on ETa estimates, and (3) application for irrigation-scale ETa mapping. The validation was conducted in the Filadelfia district (2016–2017) using 10 Landsat 8 images and EC data from the AmeriFlux “CR-Fsc” site. A systematic evaluation of parameterization schemes was performed by testing 216 combinations per image, integrating alternative methods for albedo, leaf area index, surface temperature, soil heat flux, sensible heat flux, and anchor pixel selection. Model performance was evaluated using R² and RMSE based on instantaneous ETa. The optimal configuration achieved an R² of 0.80 and an RMSE of 0.045 mm h⁻¹, revealing strong dependence of ETa estimates on parameterization. Spatial transferability is being evaluated to define the model’s radius of applicability across heterogeneous tropical conditions.