# Design Criteria for Planning the Agricultural Rainwater Harvesting Systems: A Review
## 1 Introduction
The studies trying to estimate the amount of water to be generated in floods or those seeking to supply water needs propose alternatives that start with the rainwater harvesting systems (also called water harvesting, rainwater collection system, and other names), which are made in geographical areas with arid (annual precipitation \(<\) 100 mm), semi-arid (annual rainfall 250-400 mm), monsoon (minimum monthly precipitation between 60 and 100 mm), and sub-humid (characterization depends of the location of the study area) [16] conditions. In each of these climatic conditions, rainwater harvesting projects were developed for urban and rural areas, considering the purposes for the water resources are to be used [17; 18; 19] as well as the problems to solve floods or droughts among them. Once the problem is understood, researchers have considered returning to rainwater harvesting systems as an adequate solution for flood mitigation and supply. These systems have been used in the world in the past [20], and their use has now been accentuated in arid and semi-arid zones, since these have been affected by the change in rainfall patterns. A rainwater harvesting system is a general term that is used to describe the collection and concentration of runoff or its many uses, including agricultural and domestic use [21; 22; 23]; it is also used to describe the collection and storage of water either directly in the form of precipitation and runoff, or indirectly in the form of groundwater, surface springs, or rivers [24; 25]. In addition, among rainwater harvesting systems, precipitation is the main variable to obtain the amount of water resources; therefore, the solutions proposed will depend on the study area--that is, on the physiographic characteristics and existing infrastructure (urban and rural areas). In the case of the analyses developed for urban areas, there is a problem with rainwater use, since people are skeptical of this supply mode, especially in areas with low amounts of precipitation [26]. Nevertheless, rainwater use has been successful when water is captured to help maintain the hydrological cycle and used in activities in which water that is suitable for human consumption is not required [17; 19; 27]. In the case of rural areas, which is the focus of this study, the solutions proposed will depend on the type of supply required (population or agricultural), and the area where it will be applied (arid, semi-arid, and others). Therefore, solutions are projected from the outlook that are related to offering water resources for agricultural activities and the domestic needs of farms, allowing alternatives to counteract water scarcity, among them, collection from domestic roofs [18; 26; 28; 29; 30; 31; 32], dams, cisterns, ponds [33; 34; 35; 36], ridges, furrows, and others. In many cases, these waters are not used for human consumption, as their physicochemical and bacteriological conditions do not comply with any international regulations regarding water potability, due to the presence of pollutants in rainwater and even from the roof material serving as catchment for the collection [37; 38; 39; 40; 41; 42; 43]. This research study reviews the conditions of rainwater harvesting systems in rural areas. First, methodologies for rainwater harvesting (RWH) are determined, considering the type of hydraulic structure used for runoff collection according to the basin area. Later, the type of soil, average rainfall, and physiographic characteristics are identified to constitute the most relevant design parameters for planning and suitable sites of the hydraulic structures that will guarantee an integral management of water resources (IMWR) in agriculture.