Farm reservoirs for rainfed areas

The OFR technology helps in harvesting rainwater during excess rainfall and in storing runoff water for use in dry spells

By Author K Sreenivas Reddy, A Amarender Reddy   |   Published: 5th Apr 2019   12:08 am Updated: 4th Apr 2019   9:15 pm

Water is the most important and limiting resource in rainfed areas with crop growing window restricted to only four months of monsoon, resulting in mono-crop only in the kharif season (June-Sept) in a year. Major crops grown in rainfed areas are pulses and oilseeds and coarse cereals like pigeon pea, groundnut, sorghum and cotton. The average land productivity in rainfed areas is less than 1 tonne/ha. Although rainfed areas produce less yields compared with irrigated areas, they occupy about 55% of the cropland, and have to satisfy food security needs as irrigated agriculture alone cannot address this gap.

According to scientific evidence, the rainfed areas face acute shortage of water for agriculture and drinking, resulting in farm distress, land degradation, low income and malnutrition covering almost half of the villages in India involving 6-7 crore farmers. A CRIDA (Central Research Institute for Dryland Agriculture) analysis indicated that the impacts such as short duration rainfall with high intensities, decrease in rainy days, increased dry spells immediately after germination of the crops during rainy season and shift in the occurrence of monsoon rainfall are common in these areas. Since soils are poor and the water-holding capacity is very less, most of the rainwater goes as run off with no use to cultivation of crops.

On Farm Reservoir

Rainwater harvesting is one of the best options in rainfed areas. It is a key component in agricultural production technology as a drought management strategy to enhance the livelihoods of farmers and reduce the yield gap between irrigated and rainfed agriculture.
The CRIDA has developed ‘On farm Reservoir’ (OFR) technology to harvest rainwater during excess rainfall and store the runoff water to use in subsequent dry spells. The technology has two key objectives: (i) sustainably increasing farm productivity and income in rainfed areas and (ii) increasing adaptive capacity and resilience to climate change. The dissemination and uptake of the OFR technology is still largely an ongoing, challenging process.

Live on Field

The CRIDA scientists, under the agri-consortia research platform on water, conducted experiments on field at Petrallachenu village (a chenchu tribal village) in Padara mandal of Nagarkurnool district during 2016-19. The experiment included construction of OFR for rainwater harvesting and a portable raingun system with diesel engine coupled with an integrated farming system module.

An OFR having the dimensions of 20m length, 10m width and 3.5m depth with a storage capacity of 6 lakh litres was constructed at the lowest corner of the farmer’s field (Figure 1). The design was based on the runoff coefficient values and the catchment area. The OFR was provided with silt trap, inlet and outlet. The field was remodelled with soil and water conservation measures like contour bunds and field channels connecting to the inlet of the OFR. Geomembrane of 500 microns’ thickness was used as lining material for the OFR in order to arrest seepage losses. A portable raingun irrigation system (PRIS) was designed for water application in the critical stages of the crops during dry spells. A 5-hp diesel engine pump set was used for efficient water application to the crops. The PRIS was designed with diesel pumpset along with 40 sprinkler pipes and raingun with discharge of 240 lpm (litres per minute) with operating pressure of 2.5 kg cm-2 with spraying diametre of 48 m covering an area of 1,089 m2 at a time.

Results and Impact

The OFR experiment was aimed at knowing the impact on enhanced water availability, cropping pattern change to more remunerative crops and incomes of the farmers. Cost components like that of OFR construction, irrigation system and its operation and maintenance, cost of cultivation, yield and market prices were taken into account while calculating the net returns to farmers.

The results demonstrated that the OFR technology facilitated a shift in cropping pattern from monocrop of coarse cereals to double crop, which included pulses and vegetables in addition to fodder for cattle and small ruminants. Supplemental irrigation at critical stages through the OFR too facilitated a shift in cropping pattern from short duration coarse cereals to long duration cotton, which fetch higher returns. The technology was successful in increasing farmer’s profitability in all rainfall scenarios like normal, short and long dry spell years. The OFR technology not only enhanced water availability, but also increased food and nutritional security.
The OFR provided enough water to meet two critical irrigations of main crop and 5-6 irrigations with 30 mm at weekly interval for vegetables and fodder crop in a small area. During 2016-17 (long dry spell), pulse-based farming system — which includes black gram (2.5 acre), vegetables (0.5 acre), fodder (00.125 acre) and small ruminants (10 animals) — was taken up. The net returns before the ORF was at Rs 14,000 and post OFR increased to Rs 29,100.

During 2017-18, cotton-based system (under normal monsoon) — which includes cotton (0.5 acre), vegetables (0.5 acre), fodder (0.125 acre) and small ruminants (10 animals) — was taken up. The farmer gained Rs 96,065 after OFR as against a net loss of Rs 3,600 before OFR.
Constructing an OFR requires an investment of Rs 1.75 lakh (Rs 95,000 for OFR and Rs 80,000 for irrigation system). This amount can be paid back in two-and-a-half years years (with full cost borne by farmers). If they procure at 50% subsidy, the payback period is only 1.3 years. The benefit-cost ratio increased from 0.93 to 1.67.

Scaling up

The experiments clearly shows that there is a potential for doubling the income of small farmers through the OFR technology with irrigation systems as a total package. Popularisation of OFR is essential to store and use of runoff water in rainfed areas by supplying water during dry spells. There are 6-7 crore rainfed farmers and the OFR technology could help in meeting the twin national objectives of doubling farmers’ income and conserving soil and water.

There is also a need for subsidising at least 50% of the initial capital cost, which comes to only Rs 87,500. The remaining 50% of can be divided between labour and cost in equal proportion. The labour component can be funded through MGNREGA and the remaining Rs 43,750 can be either borne by farmers or financed through banks. In addition, the OFR could be promoted for water resource development and enhancing water productivity at the field level to alleviate drought under PMKSY.

(The authors are Principal Scientists, ICAR-Central Research Institute for Dryland Agriculture, Hyderabad)