EXTENDED ABSTRACT
Introduction:
Drylands, which account for about 40% of the Earth’s land area, are of great importance globally (Cherlet et al., 2018). A large part of the world’s population also resides in these areas, and these areas play a major role in providing a significant portion of food and environmental services such as climate regulation, water supply, and other issues (Eldridge et al., 2024). However, erosion and subsequent reduction of soil nutrients and consequently its fertility are one of the challenges facing developing countries, especially in drylands. Such a situation threatens the food security of these areas and accelerates the occurrence of erosion, dust phenomena, floods, and droughts (Saayman et al., 2017). Although soil erosion is a natural phenomenon on the earth's surface, its intensity and development in natural areas pose many problems. Several factors such as soil characteristics, climate, roughness, wind speed and vegetation cover play a role in soil erosion, the most important of which is vegetation cover (He et al., 2011). The main reason for the difference in erosion in dry and wet areas is the lack of vegetation cover in dry areas (Suter-Burri et al., 2013). By increasing the roughness of the soil surface, vegetation prevents the direct impact of wind and rain energy on the earth's surface, which consequently reduces evaporation and maintains soil moisture, and ultimately reduces soil erosion.
Methodology:
To do this research, locations where excavations for road construction had been carried out and which were prone to collecting runoff were identified. During field visits, 12 reservoirs where runoff from micro-catchment entered were selected one by one. Then, the dimensions and volume of water extracted were measured. Two soil samples were taken from the location of these reservoirs and their salinity, acidity and texture characteristics were tested. The vegetation status of these reservoirs was also examined. In addition, in order to economically evaluate the water stored in micro-catchment reservoirs, considering the labor wage situation, the cost of water tanker transportation, the non-potable water sales rate in the region, as well as cost data resulting from the implementation of research works in the region, the cost of watering seedlings in the research area was estimated and compared with the micro-catchment.
Results and Discussion:
The results of soil sample tests in the study area showed that the soil quality of the area is low and its fertility is low. However, it is suitable for the growth of resistant and saline plants. The investigation of the dimensions and water intake status of micro-catchment reservoirs showed that the length and width ranges of the structures are 4.5 and 12.3, 3.2 and 5.5 meters, respectively. The average length and width of the investigated pits are also 6.6 and 4.2 meters, respectively. The depth of the structures fluctuated between 0.9 and 1.3 meters, with an average depth of 1.1 meters. The amount of water collected in the studied reservoirs due to rainfall was 1.404 cubic meters, with an average contribution of 33.7 cubic meters for each of them. Given the scarcity of water in the Sistan region and even its absence in an area such as the location of this study, the performance of micro-catchment has high economic, environmental, and security value. A survey of the study area shows that this area is flat, level, and has a very gentle slope with a hard surface layer that prevents water from penetrating the soil. Although the rainfall in the area is low, even this insignificant amount of rainfall accumulates on the surface of the ground for several days due to the lack of permeability of the soil, and over time, it evaporates and becomes unavailable without being used. Creating pits at the end of each slope of these areas with a water capacity based on the size of those areas will turn them into micro-catchments, which will increase water penetration into the soil. In this regard, Milton and Coetzee (2022) have also reported that micro-catchment increase soil moisture, which makes water easily available to plants and provides a basis for their growth. The results also showed that the great depth of the pits has a negative effect on the establishment of vegetation.
Conclusion:
Low precipitation—compounded by unfavorable temporal and spatial distribution and high evaporation rates in arid regions; has led to a water scarcity crisis and limited access to sustainable water resources. This study aimed to evaluate the impact of small-scale catchment areas on seasonal runoff harvesting by assessing the volume of water collected in storage reservoirs constructed in the hyper-arid region of Shahre Sokhte, Sistan. The results indicated that, despite low precipitation in the study area, runoff from seasonal rains accumulated on the flat terrain due to an impermeable surface layer; however, the recent construction of numerous pits has allowed for the storage of significant volumes of this runoff, thereby supplying the necessary moisture to plants and facilitating the restoration of vegetation in the area. An assessment of the economic value of this harvested runoff in the study area revealed that constructing these pits significantly reduces the cost of supplying water for seedling-planting projects; this underscores the effectiveness of such small-scale catchment structures in harvesting and managing surface runoff within the hyper-arid Sistan region. Overall, the findings indicate that constructing small-scale water-harvesting systems—given their low cost and economic viability represents a compatible and efficient approach to managing and storing surface runoff in hyper-arid regions like Sistan. Extending this approach to other parts of the region would not only allow for the utilization of these water resources to meet plant water requirements but also create a favorable foundation for restoring vegetation cover and improving environmental conditions.
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