Runoff Farming System Information for Beginners

Introduction to Runoff farming:

Runoff farming is basically the use of water harvesting to grow a “crop.” A section of the land is sacrificed. For the water, it yields to create a crop on the run on the area. The collected water generally is all stored in the soil profile of. Runoff may be harvested from roofs & ground surfaces as well as from intermittent or ephemeral watercourses.

Runoff is water from rain, melted snow, or irrigation that is not absorbed & held by the soil but runs over the ground and through loose soil. As the runoff moves, it picks up & carries pollution. It can then deposit the pollution into ponds, lakes, coastal waters, & underground sources of drinking water.

Water harvesting in agriculture (runoff farming):

“Runoff farming” is the same with “Water Harvesting but for Irrigation functions”. When the harvested runoff water from un-cropped areas is directed to a cropped area, this technique is known as runoff farming. Soil profile acts as a water storage container, but storage in ponds or cisterns is feasible. Factors affecting the capacity of soil storage are the depth of the soil profile, depth of plant roots, texture, structure, infiltration rate & the water holding capacity of the soil. The catchment-to-field ratio can vary from 1:1 and from 1: many square kilometers. The higher the aridity of an area, the larger is the necessary catchment area in relation to the cropping area for the same water yield.

Some information about Runoff farming:

We have been evaluating runoff farming as a management tool to try to improve the productivity & profitability of marginal land in the Southwest. In our studies, runoff farming was used to grow conifer trees on, particularly marginal land. Two sites on Forest Service land near Camp Verde, Arizona, were converted from assorted cactus, creosote bush, catclaw & weeds to stands of Arizona cypress and Eldarica pine. This area has a standard annual precipitation of 12 inches, but potential evaporation of five times that amount.

Two runoff farming water harvesting groups are generally recognized by

1. Rainwater harvesting 2. Floodwater harvesting.

Rainwater harvesting can be extra divided into 1. Micro-catchment and 2. Macro catchment runoff farming types.

Floodwater harvesting can also be divided into 1. Within streambed and 2. Through diversion runoff farming types.

Micro-catchment runoff farming is a procedure of bringing together surface runoff from a small catchment area and storing it in the root zone of an adjacent infiltration area. Macro catchment runoff farming method is referred to by some authors as “runoff farming water harvesting from long slopes”, as “medium-sized catchment water harvesting” or as “harvesting from external catchment systems”. Runoff farming with floodwater harvesting comprises systems with catchments being square kilometers in size, from which runoff water flows through a major wadi, the water is forced to infiltrate & the wetted area can be used for agriculture or pasture development. Runoff farming requires moderately large labor inputs and land. Low-cost efficient use of runoff farming in arid zones for food and fuel production could help to restore self-sufficiency in food production for local populations in several dry regions. Countries, where this method has been used, include Egypt, Tunisia, Libya, & southern Algeria. Some other countries outside Africa include Isreal, Jordan, North Yemen, India, Pakistan & the Soviet Union.

There should be global cooperation between scientists & practitioners involved in water harvesting and runoff farming. By learning from failures & successes, a high degree of sustainability might be reached, similar to the one which apparently existed in the past thousands of years. Runoff farming has confirmed to be a precious tool particularly in dry marginal areas to increase crop yields and reduce crop risk, to improve pasture growth, to boost reforestation, to permit a higher degree of food production, to fight soil erosion, to make best use of available water resources, to suppress soil salinity and, in a few cases and to recharge the local groundwater.

According to Nasr (1999), there are 2 basic types of runoff-farming systems: first, the

* Direct water application system, where the runoff water is stored in the soil of the crop growing area during the precipitation, & second, the

* Supplemental water system, where the collected water is stored offsite in some reservoirs & later used to irrigate a certain crop area.

As also according to Critchley and Siegert (1991), normally, two runoff farming water harvesting groups are generally recognized, rainwater harvesting and floodwater harvesting.

Rainwater harvesting runoff farming:

1. a) Micro-catchment Runoff farming water harvesting (MIRFWH) scheme:

Micro-catchment runoff farming water harvesting is a process of collecting surface runoff from a small catchment area and storing it in the root zone of an adjacent infiltration area or basin. This infiltration area or basin may be planted with annual crops, or with a single tree or bush.

The advantages of MIRFWH systems are:

* Simple to design and cheap to install, therefore easily replicable & adaptable.

* Higher runoff efficiency than medium or large scale water harvesting scheme no conveyance losses.

* Includes erosion control.

* Can also be built on almost any slope, including almost level plains.

The disadvantages of MIRFWH systems are:

* The catchment utilizes potentially arable land.

* The catchment area has to be preserved, i.e. kept free of vegetation which requires a comparatively high labor input.

* If overtopping takes place during extremely heavy rainstorms, the systems may be irrevocably damaged.

1. b) Macro catchment runoff farming water harvesting system:

Macro catchment runoff farming scheme is referred to by some authors as “runoff farming water harvesting from long slopes”, as “medium-sized catchment water harvesting” or as “harvesting from external catchment systems”. It is differentiated by as:

* The predominance of turbulent runoff & channel flow of the catchment water in comparison to sheet or rill flow of micro-catchments.

* The limited area contribution phenomenon which is not relevant for micro-catchments.

* The catchment area has an inclination of 5 % to 50 %; the cropping area is either terraced or located in flat terrain.

Floodwater harvesting runoff farming:

Runoff farming with floodwater harvesting comprises systems with catchments being several square kilometers in size, from which runoff water flows through a major wadi, necessitating more complex structures of dams and distribution networks. It is called ‘Large catchment water harvesting’ or ‘spate irrigation’ comprises two forms. Floodwater harvesting runoff farming can be divided into two types:

1. Floodwater harvesting within the stream bed, water flow is dammed &, as a result, inundates the valley bottom of the flood plain. The water is forced to infiltrate & the wetted area can be used for agriculture or pasture improvement.
2. Floodwater diversion, wadi water is forced to leave its natural course & conveyed to nearby cropping areas. These systems the catchments being several square kilometers in size require more complex structures of dams & distribution networks and a higher technical input than the other two water harvesting methods.

Runoff rainwater harvesting:

In this process of collecting rainwater for irrigation, water flowing along the ground during the rains will be collected in a tank below the surface of the ground. The tank is creating using bricks, which are coated with cement. During storage, it is important to incorporate proficient & effective water conservation methods by reducing evaporation and also by adopting efficient irrigation techniques. It is very ‘easy to adopt’ technology proven with many communities in the country that if used properly can be extremely profitable.

Step-by-step procedure of runoff rainwater harvesting:

• Selecting a location for the building of a rainwater harvesting tank
• Observe the course of the surface flow of rainwater in the land.
• Even though some believe that such tanks should be constructed in the lowest lying area of the land, this is not effectively so. Due to the seasonal patterns of rainfall & the high intensity of rains received in Sri Lanka, it is possible to fill a 12,000-liter capacity tank without much difficulty.
• The tank may be subjected to cracking due to the root zone activities, so, it is advisable not to construct the tank in close proximity to large trees.
• The tank must be close to the area of cultivation to ensure ease of irrigation.
• The tank should not be in close proximity to the house or to paths or roadways as it is possible for children and even negligent adults to fall in. As an additional security measure, build a fence around the tank.
• The opening of the tank should be in the direction of the run of rainfall. It is not advisable to obstruct patterns of natural flow of water as there is a possibility of mud & other waste getting into the tank. (The mud filters function only when the water flows straight through them).

Things to be considered:

• If an extremely strong current of water is flowing it could place the tank in jeopardy.
• If by a construction of the tank, the natural water flow is obstructed, soil erosion can occur & crops can consequently be destroyed.

Constructing the Runoff rainwater harvesting tank:

• Clear the chosen land thoroughly. Flattening the land is mainly for ease of taking measurements.
• It is advisable to build a circular tank as it will withstand greater pressures.
• Determine the quantity of water necessary for irrigation purposes.

In such instances, the below factors should be considered;

a.) The rainfall model of the area. (If the area experiences standard rainfall during the year, a small tank of 4000 liters-5000 liters would suffice, whereas in mainly dry areas which experience dry spells for about 6 months of the year, it would be helpful to store as much water as possible.)

1. b) The extent of land, which is planned to be cultivated
2. c) The quantity of investment that can be made.

Read: Rooftop Farming Procedure.

Agricultural Runoff:

Agricultural Runoff is water sent from farm fields due to irrigation, rain, and melted snow. This runoff water can have fertilizers, pesticides, animal waste, or soil particles, which can enter and contaminate sources of drinking water.

Agricultural Runoff has been a growing issue for lakes & rivers. As pollutants run off farm fields, they find their way into rivers and streams that finally end up in drinking water. Water treatment centers have to use millions in purchasing chemicals to remove runoff from farms, so it is safe for human consumption.

Agricultural runoff is surface water leaving cultivated fields as a result of getting water in excess of the infiltration rate of the soil. Excess water is due mainly to precipitation, but it calls conic from irrigation and snowmelt oil soils. Also, there is considerable concern about the erosion of cultivated fields due to the rainfall & runoff processes, primarily related to the loss of valuable topsoil from the fields and subsequent losses in productivity.

The potential for pollution of surface waters such as rivers & lakes due to agricultural runoff has been recognized and the nature and extent of such pollution are systematically assessed. Agricultural runoff is grouped into the group of non-point source (NPS) pollution because the potential pollutants originate over large, diffuse areas and the exact point of entry into water bodies cannot be precisely identified. These sources of pollution are mainly problematic in that it is difficult to capture and treat the polluted water before it enters a stream. The point sources of pollution, such as municipal sewer systems typically enter the water body via pipes and it is comparatively easy to collect such water and reroute it through a treatment scheme prior to releasing it into the environment. Because of the NPS environment of agricultural runoff, efforts to eliminate pollutants are focused on practices to be applied oil near cultivated fields themselves. Agricultural runoff is considered to be the primary source of pollutants to streams & lakes, as well as estuaries. Runoff farming from agricultural fields begins soil, organic matter, manure, fertilizer & pesticides into small streams, increasing the volume of stream discharge and changing water quality. Researchers such as Cooper have reviewed the acute toxic & sub-lethal chronic effects of such runoff, and have identified pesticides as one of the major stresses of aquatic communities.

Pesticides in agricultural Runoff:

Insecticides, herbicides, and fungicides, though used to kill pests & control the growth of weeds and fungi, call the water through direct application, runoff, wind transport, and atmospheric deposition, killing fish and wildlife, poisoning food sources, & destroying animal habitats. Such NPS contamination from pesticides can be reduced by applying the IPM method based on oil specific soils, climate, pest history, and crop selection for a particular field. IPM helps limit pesticide use & manages necessary applications to minimize pesticide movement from the field. Although relatively small herbicide loads are accepted by surface runoff water in relation to the amount applied to a cultivated field (from less than 0.5% up to 5%), their residues call serious environmental risks. The main pathway for herbicide losses is the surface runoff, & a rainstorm shortly after application, call high chemical concentrations in the runoff, wreaking serious consequences for water quality and wildlife habitats. Vegetative filter strips (VFS) have been planned as a means to reduce surface water contamination caused by agricultural NPS. A VFS acts as a natural dam or terrace and, by reducing runoff, the water has more time to penetrate & incorporate the pollutants in the soil and thus prevent off-site movement. Also, VFS alters flow hydraulics, reducing runoff speed & increasing water infiltration. The filter thus enhances sediment deposition and filtration by vegetation, pollutant adsorption into the soil and dead & living plant materials, and uptake of soluble pollutants by plants.

Infiltration was found to be the mainly important herbicide removal mechanism associated with VFS, especially for soluble or weakly adsorbed pesticides. Watanabe and, investigating diazinon transport within a VFS, found that the pesticide was trapped on its surface & in the root-zone, where further adsorption, attenuation and presumably degradation may occur. However, enhanced infiltration could cause more leaching, allowing the herbicide to reach the water table, varying the ecotoxicological impact from the surface to subsurface water. Delphin and Chapot evaluated this leaching and investigated the fate of atrazine & de-ethylatrazine transported in runoff effluents and trapped by a grass filter strip.

The plants in the VFS conferred higher organic-matter, the substance to the filter zone than in the adjacent cultivated fields. This organic matter accumulation boosted the adsorption capacity & microbial activity for herbicide degradation, thereby reducing the amount of herbicide in surface runoff and leaching water. Higher herbicide dissipation in the VFS soil is due both to enhanced degradation & the formation of non-extractable (bound) residues, which can become a long-term sink inside the filter.

Pollutants from agricultural runoff include:

• Heavy metals
• Herbicides
• Nutrients such as nitrogen & phosphorus
• Pesticides
• Salts
• Soil Particles

Uses of Runoff farming:

Livestock Applications:

Runoff farming is used to grow trees for summer shade and shelterbelts used for winter storm protection. The runoff farming systems also are designed to channel some of the harvested water into a storage reservoir for drinking water supplies. Runoff farming is being used in some parts of the world to supply emergency livestock feed during severe droughts. Opuntia and saltbush have been used, but many other drought-tolerant evergreen browses plants such as jojoba, kochia & winterfat could be likely candidates.

Conservation and Wildlife Applications:

Runoff farming can be used to develop wildlife habitats. Plants could be chosen for the particular food, cover & nesting requirements of specific wildlife species. The system also is used to supplement animal drinking water supplies.

Aesthetic Applications:

Runoff farming can be used to improve landscaping around ranches, and to revegetate abandoned irrigated cropland & mine spoils in some arid-semiarid areas. Combined with mosaics of small woods, this also is ideal for wildlife.

Improving Productivity:

Our studies were with evergreen conifer trees, but there are a number of potential uses for runoff farming to develop the productivity of some of our semiarid lands where water is a limiting factor. Runoff farming could be used in some areas for marketable or food crops where irrigation is not an option. High-value crops either tried or suggested for Runoff farming contain grapes, berries, various fruit and nut species, Indian corn, and asparagus.

Runoff farming is a centuries-old agricultural system designed especially to increase the productivity of arid-semiarid lands. The use of Runoff farming is growing throughout the world but has been slow to catch on in the United States. Normally, the system has languished in the shadow of irrigated agriculture, but this may change as irrigation waters dry up or become prohibitively expensive and as population pressures around the world force additional demands on marginal lands.

Read: Growing Cowpeas, Cultivation Practices.

Last Updated: February 18, 2019