Innovatory rainfall simulator design – A concept of moving storm automation

We developed an advanced design programmable rainfall simulator (RS) to simulate a moving storm rainfall condition. The RS consists of an automated nozzle control system coupled with a pressure regulator mechanism for an operating range of 50 kPa to 180 kPa at a drop height of 2000 mm above the soil flume surface. Additionally, a programmable mobile application was developed to regulate all RS valves. Near natural rainfall conditions were simulated at varying spatial and temporal resolutions in a controlled environment. A soil flume of 2500 mm × 1400 mm × 500 mm was fabricated to conduct different hydrological experiments. The flume was designed to record overland, subsurface, and base flows simultaneously. This study focused on a detailed analysis of moving storms and their impact on hydrograph characteristics. Experimental results showed a considerable difference in terms of time to peak (tp), peak discharge (Qp), and hydrograph recession for two different storm movement directions (upstream and downstream). Two multiple regression models indicate a statistically significant relationship between the dependent variable (tp or Qp) and the independent variables (i.e. storm movement direction, storm velocity, and bed slope gradient) at a 5 % level of significance. Further, the impact of these moving storm phenomena reduces with the increase in the storm movement velocity.

Influence of drop size distribution and kinetic energy in precipitation modelling for laboratory rainfall simulators

It is difficult to define the hydrologic and hydraulic characteristics of rain for research purposes, especially when trying to replicate natural rainfall using artificial rain on a small laboratory scale model. The aim of this paper was to use a drip-type rainfall simulator to design, build, calibrate, and run a simulated rainfall. Rainfall intensities of 40, 60 and 80 mm/h were used to represent heavy rainfall events of 1-hour duration. Flour pellet methods were used to obtain the drop size distribution of the simulated rainfall. The results show that the average drop size for all investigated rainfall intensities ranges from 3.0–3.4 mm. The median value of the drop size distribution or known as D50 of simulated rainfall for 40, 60 and 80 mm/h are 3.4, 3.6, and 3.7 mm, respectively. Due to the comparatively low drop height (1.5 m), the terminal velocities monitored were between 63–75 % (8.45–8.65 m/s), which is lower than the value for natural rainfall with more than 90 % for terminal velocities. This condition also reduces rainfall kinetic energy of 25.88–28.51 J/m2mm compared to natural rainfall. This phenomenon is relatively common in portable rainfall simulators, representing the best exchange between all relevant rainfall parameters obtained with the given simulator set-up. Since the rainfall can be controlled, the erratic and unpredictable changeability of natural rainfall is eliminated. Emanating from the findings, drip-types rainfall simulator produces rainfall characteristics almost similar to natural rainfall-like characteristic is the main target.

Prediction of S12-MKII rainfall simulator experimental runoff data sets using hybrid PSR-SVM-FFA approaches

Effective prediction of runoff is a substantial feature for the successful management of hydrological phenomena in arid regions. The present research findings reveal that a rainfall simulator (RS) can be a valuable instrument to estimate runoff as the intensity of rainfall is modifiable in the course of an experimental process, which turns out to be of great advantage. Rainfall–runoff process is a complex physical phenomenon caused by the effect of various parameters. In this research, a new hybrid technique integrating PSR (phase space reconstruction) with FFA (firefly algorithm) and SVM (support vector machine) has gained recognition in various modelling investigations in contrast to the principle of empirical risk minimization through ANN practices. Outcomes of SVM are contrasted against SVM-FFA and PSR-SVM-FFA models. The improvements in NSE (Nash–Sutcliffe), RMSE (Root Mean Square Error), and WI (Willmott's Index) by PSR-SVM-FFA over SVM models specify that the prediction accuracy of the hybrid model is better. The established PSR-SVM-FFA model generates preeminent WI values that range from 0.97 to 0.98, while the SVM and SVM-FFA models encompass 0.93–0.95 and 0.96–0.97, respectively. The proposed PSR-SVM-FFA model gives more accurate results and error limiting up to 2–3%.

A Temporally Varied Rainfall Simulator for Flash Flood Studies

Experimental studies of flash floods require rainfall simulations. For this reason, various rainfall simulators have been designed, built, and employed in previous studies. These previous rainfall simulators have provided good simulations of constant rainfall intensities; however, these simulators cannot generate temporally varied rainstorms. Thus, the effect of the temporal distribution of a rainstorm on flash flooding cannot be studied using current rainfall simulators. To achieve accurate and reliable results in flash flood studies, simulating rainstorms that are similar to natural precipitation events is essential, and natural rainfall varies temporally. Thus, a rainstorm simulator was designed and built using cascading tanks to generate rainstorm hyetographs that cannot be obtained using traditional rainfall simulators. The result of the rainstorm generated by the proposed instrument and its numerical model showed that the instrument can simulate the temporal distributions of rainstorms with an accuracy of 95 percent. Consequently, the proposed instrument and its numerical model can be applied for generating artificial rainstorm hyetographs in experimental and field studies of flash floods.

Analisis Debit Limpasan dan Indeks Erosivitas Hujan pada Metode USLE Akibat Variasi Intensitas Hujan dengan Alat Rainfall Simulator

Terjadinya hujan mengakibatkan banyak sekali hal, misalnya aliran permukaan dan juga erosivitas hujan. Energi hujan tersebut bisa membuat suatu lahan tererosi. Dalam penelitian ini bertujuan untuk mengetahui pengaruh variasi intensitas hujan terhadap debit limpasan yang dihasilkan, indeks erosivitas hujan, dan besar laju erosi dengan metode USLE pada alat rainfall simulator. Pengambilan sampel tanah di Desa Pandesari, Kecamatan Pujon, Kabupaten Malang. Studi ini dilakukan dengan variasi hujan yaitu 0,5 liter/menit, 1,0 liter/menit, 1,5 liter/menit, dan 2,0 liter/menit dengan kemiringan alat rainfall simulator sebesar 5%. Hasilnya, intensitas hujan sangat memengaruhi debit limpasan pada alat rainfall simulator, dengan koefisien determinasi R2 = 0,981. Intensitas hujan juga memengaruhi erosivitas hujan pada rainfall simulator dengan koefisien determinasi R2 = 0,999. Dan pada metode USLE, laju erosi yang dihasilkan dipengaruhi juga oleh intensitas hujan dengan koefisien determinasi R2 = 0,999.

Fabrication and study of laboratory scale rainfall simulator for soil erosion assessment

A rainfall simulator is an ideal tool for infiltration, soil erosion and other related research areas for replicating the process and characteristics of natural rainfall. The present paper describes the design of a comprehensive rainfall simulator. In this study a laboratory scale rainfall simulator is developed, which is particularly meant for the assessment of soil erosion at plot scale by considering various soil grain types, soil slope angles and surface exposures under different rainfall conditions. The Rainfall characteristics including the rainfall intensity and its spatial uniformity raindrop size and kinetic energy confirm that natural rainfall conditions are simulated with sufficient accuracy. The comparative measurement was carried out in a laboratory using rainfall simulator fabricated of 4 feet length and 2.5 feet width, where the applied slope angle is 3% with 39 mm/hr rainfall intensity. The runoff and soil loss for different samples were assessed by conducting number of trials. From the results it was found that the soil tilled and keeping it as a bare plot is more prone to runoff compared to soil without tilled and straw mulching has helped to reduce the runoff by 57% as compared to soil without mulching.

PERBANDINGAN INDEKS ERODIBILITAS TANAH YANG DITETAPKAN DENGAN METODE WISCHMEIER DAN RAINFALL SIMULATOR

Land use in the upstream area of the Brantas watershed, including that in Tawangsari village, Pujon District of Malang Regency, has undergone significant changes. The conversion of forest to moor, plantations, and settlements has resulted in decreased soil quality leading to soil degradation. The purpose of this research was aimed to compare the soil erodibility index determined by the rainfall simulator with Wischmeier methods. The results showed that there was a relationship between the results of the soil erodibility value using the Wischmeier method with land use and slopes based on the correlation and regression values caused by the physical properties of the soil. There were differences in soil erodibility index with the Wischmeier method and the Rainfall Simulator method, namely the average agroforestry results of 0.108 and 0.112 and an average of 0.152 and 0.147 moor. The use of the Wischmeier method is more recommended.