Investigation of the effect of different surfaces of rainwater catchment on runoff production and erosion control

Optimal use of rainfall in arid and semi-arid regions can play an important role in meeting the water needs of green space in low water seasons. On the other hand, poor vegetation can cause erosion and destruction in sloping lands that can be partially resolved if water and soil resources are properly managed. Rainfall is one of the most important sources of water supply for various uses. One of the methods of collecting rainwater is to make the ground impermeable and to maximize rainwater runoff. Impermeable surfaces can exist naturally like rock surfaces, or can be artificially created by covering the ground with materials such as asphalt, concrete, insulation sheets such as plastic, geomembrane and decamond. This study, which was carried out in the northern part of Tabriz, was conducted in four treatments, each with three replications of 4 m2 (2m×2m), including geomembrane cover area, plastic cover with sand protection, natural surface and natural surface with sand mulch. Results of 78 rainfall events over two years showed that in intermediate slopes of 33-38.6%, runoff from rainfall for geomembrane, plastic cover with sand protection, natural surface and natural surface with sand mulch were 84, 67, 3 and 2% of rainfall respectively and rainfall threshold for runoff at mentioned surfaces was 0.28, 2.56, 9.95 and 11.12 mm, respectively. Therefore, with respect to annual normal rainfall (245.7 mm), the volume of runoff accumulated for geomembrane, plastic cover with sand protection, natural surface and natural surface with sand mulch will be 206, 164, seven and five Lm-2 ina year, respectively. Comparing the means, the geomembrane cover treatment was identified as a suitable option for runoff production. Also, sand mulch on the natural surface reduces soil erosion from 97 to 9.5 grm-2 in two years.