Portable Rainfall Simulator A Participatory Action Learning tool to understand desertification process

Subba Reddy, H.P.Singh, Christine King and Sreenath Dixit

 Soil erosion by runoff is the principle cause of land degradation particularly in the rainfed agro-eco regions of India. Consequences of land degradation could be more disastrous in arid and semi-arid areas where the eco system is very fragile. Rainfall being the only source of sustaining the entire production system, these areas chronically suffer from low food and fodder productivity due to poor and erratic rainfall. The process of land degradation is very dynamic and complex at times. Unfortunately, more often than not it goes unnoticed by the very people dwelling in such less-endowed areas which are already marginalised. The people are characterised by low literacy and awareness levels, poor socio-economic status and have low risk bearing ability. Lack of awareness about the process of land degradation and inadequate technological interventions to manage it are the major bottle-necks for community mobilisation against land degradation.

In the past, government interventions for combating land degradation without peoples involvement have failed miserably. There is now a greater realisation about the need for peoples’ participation in such endeavours.  Peoples’ participation in any community based development activity involves a considerable element of community education. Such efforts should take into consideration the principles of adult learning and involve simulations of real life situations so that the learning is easy and quick. Once the community is convinced about their role in the programme the rest will follow suit at a fairly faster pace. Rainfall simulator is one such tool that aids action learning process among village communities to understand the complex nature of runoff driven erosion of soil, the chief cause of land degradation. The principle involved in action learning through rainfall simulator is simple. Hardly any farmer takes the opportunity to watch the effect of rain water impact on soil when it rains for one would run for shelter the moment it starts raining! Therefore, when the rainfall is simulated in real field conditions, farmers can witness the series of consequences of a supposedly  ‘harmless’ rainfall event.  The velocity of raindrops, their impact on soil particles, the resultant runoff that carries the quintessential soil along, can be observed by the farmers to appreciate the damage done to their agricultural fields in one single storm.

Rainfall Simulator – An Action learning tool to understand land degradation

The rainfall simulator is a mobile gadget developed by Australian Centre for International Agricultural Research (ACIAR) that produces rainfall with a drop size and energy similar to that of natural rain. Rainfall is applied to two adjacent plots with two different but comparable treatments (Fig. 1). The plots are separated by a barrier to maintain independence between the treatments. Rainfall is usually applied at a known rate so that it can be measured for the duration of the activity. Runoff collected at the bottom of each plot is vacuumed into measuring tank where it can be easily seen and measured. Thus the device can be effectively used as a demonstration tool to promote initial interest among farmers about adverse impact of rainfall on soil, and motivating them about the need for capture and storage of rainwater in the soil. As an action learning tool, it can increase the farmers knowledge about soil and water relationships, allow them to use their experience in this context, test and review options through selection of treatments. In all, it is a multi-purpose and multi-outcome action  learning tool. Following steps are normally adopted in involving the farmers through the action learning process by using the rainfall simulator.

 The Process

The key elements in the process of simulating rainfall include (1)multi – channel publicity prior to the event, (2) participants nominate the treatments(plan), (3)participants actively construct the treatments chosen (act), (4) rainfall is applied (act), (5)monitoring of the effects by the participants(observe), (6) small group discussions (reflect). The process of self learning among participants is facilitated by the scientists.

 Planning and  execution

The action learning groups under the leadership of CRIDA, Hyderabad used the rainfall simulator as an  action learning tool at Nallavelli, Pampanur (Andhra Pradesh) and Madhubavi(Bijapur district of Karnataka). The key concept of the field process was to ask the farmers to suggest the treatments, to enrich their participation by constructing the treatments and, set-up and discuss the cause and effect of events.  Scientists acted as facilitators to help farmers learn for themselves the working of rainfall simulator and the process of runoff  and soil loss.

Farmers’  participation

  • The Rainfall Simulator attracted both farmers and farm women. The participants liked the opportunity to participate, test their ideas particularly with respect to traditional practices. The tribal farm women involved themselves actively in selecting the treatments. Modifications were carried out after a good deal of debate. In fact the selection and application of treatments always inspired positive and willing debate
  • Farmers were encouraged to suggest other strategies as per their choice to test with rainfall simulator. The equipment created lively discussion on management practices to control soil loss and improve soil water intake.
  • Farmers measured infiltration by using a metal probe or digging with a shovel/ mattock.
  • Farmers measured runoff by comparing amount and level of water in vacuum drums.
  • Farmers took the colour of water as an indicator of sedimentation and soil loss in vacuum drums.
  • Farmers and scientist both learned by way of watching the visual impact of the raindrops on soil.
  • Farmers enthusiastically helped set up rainfall simulator as well as implementation of treatments.
  • The rainfall simulator as a tool proved successful in creating thorough discussion on management practices to control soil loss.
  • Farmers found it interesting to vary rainfall intensity during the activity in order to replicate rainfall patterns.


  • Provision of water at farmers fields is a limitation.
  • Planning the best time to hold the activity is critical eg., avoid time clashing with important social, farming and household requirements practices (such as picking children up from school)
  • Since considerable time for net working with participants is required, advance planning is necessary.
  • Facilitating a reflection period among the participants at the end of the activity is warranted.
  • It is often hard and for scientists to operate in facilitation mode and not impose their own ideas on selection or design of treatments.


  • The experiences using the rainfall simulator revealed that it is a powerful extension tool. It motivates farmers to screen various technological options for sustainable soil management and allows them to test their own ideas in a group participatory process.
  • The key factor to the success of the action learning process with the rainfall simulator as a decision making tool was to avoid the domination of the activity by scientists, and allowing farmer participants to work it out and learn for themselves.
  • The Rainfall Simulator needs to be supported by other extension processes and activities. When used as an extension tool on its own it does not consider a systems approach but focuses on soil surface treatments, runoff, infiltration and land management. For example:
  • Crop stubble may have a good impact on increasing infiltration and reducing runoff, but may not be available with most farmers due to competing use for animal husbandry.
  • Farm yard manure may be a valuable source of mulch and useful in decreasing runoff by increasing infiltration besides improving soil fertility. But the quantity required to achieve this may not be available.
  • The results from the rainfall simulator are applicable to small plots only. This often means farmers try and replicate whole field conditions on a small scale, which limits the validity of results.
  • Farmers can find it frustrating as they are unable to consider changes in fallow treatments over a greater period of time and their inability to modify rainfall intensity to more accurately reflect the storm conditions.
  • There is good potential for further action learning in extension programs. This hypothesis is supported by the fact that active involvement of farm women was obtained in all the rainfall simulator activities conducted so far. Such activities need to be sensitive to sociological issues in each community.

 Epilogue: Control of land degradation i.e. desertification  – whether through runoff, wind action, chemical factors or land abuse by farmers – is central to the sustainability of rainfed agriculture in India and many other developing countries. Many a times, the small land holders who constitute the dominant section of farmers in these regions, are either unaware of appropriate management options or are desperate in causing degradation for instance by cultivating marginal lands, or removing natural vegetation for meeting their fodder and fuel requirements. Development of technological option must therefore consider both the process of degradation and socio – economic conditions of the land holders. In order to realise this, farmers’ involvement as equal partners from the word ‘go’ is absolutely necessary. In order to realise this,  farmers must see for themselves the magnitude of land degradation (eg. soil erosion) and learn the gravity of the situation. Portable rainfall simulator has proved as a strong and effective tool in this context and can thus act as a stepping stone for farmers’ willing involvement in on-farm research/development programme in a real participatory mode, for sustainable watershed management in rainfed areas.

 Table 1. Observations recorded with the help of farmers in rainfall simulator demonstration(summer)

Centre     Comparisons Parameters
    Wetting front of soil (cm) Runoff volume(1)
Nallavelli, Hyderabad Bare soil 11.63 54.43
 Paddy straw mulch 17.65 38.96
Grazed grass cover(60%) 21.26 31.88
 Non-grazed grass cover (85%) 18.6 6.77
Furrows along the slope 11.8 43.31
 Furrows across the slope 12.7 20.56
Pampanur, Anantapur Ploughing and harrowing along the slope 26.6 21.5
Ploughing and harrowing across the slope 39.3 17
Ploughing across the slope + No FYM 17.5 16.5
Ploughing across the slope + FYM(10 t/ha) 22.6 5.2
Madhubavi, Bijapur Straw mulch (95% cover) 20 35.6
Straw mulch (100% cover) 23 16.6
Ploughing and harrowing along the slope 21 40.3
Ploughing and harrowing along the slope 22 39.5


Table 2: Results of  rainfall  simulator in standing crops during rainy season

Centre/ Place Test crop Comparisons Wetting depth (cm) Runoff(%) Soil loss 10-2 t/ha Deep drainage(mm)
Hyderabad, HRF Castor Farmers’ practice 10.9 47.8 62 26.1
Gliricidia mulch 28 47.5 26 26.3
Greengram incorporation 12.56 26.3 12 36.8
Nallavelli Hyderabad Sorghum + Pigeonpea Farmers’ practice 20.7 37.2 33 31.4
Conservation furrows 28 13.4 28 43.3
Gliricidia mulch 32.7 3.5 4 48.3
Anantapur RRS Groundnut Farmers’ practice 19.8 26.58 49 36.7
Gliricidia mulch 24.6 21.8 24 39.1
Conservation furrows 28 21 3.6 39.5
Anantapur, Pampanoor Groundnut No FYM 26 8.5 35 45.7
FYM @ 5 t/ha 28 21 3.6 39.5
Bijapur, RRS Rabi Sorghum Farmers’ practice 17.32 86.28 20.7 6.86
FYM @ 5 t/ha 28 55.42 7.5 22.28
Sunhemp incorporation 25.3 23.99 14.7 26.01
Sorghum stubbles 24.66 21.77 7 39.42
Madhubavi Bijapur Rabi sorghum Farmers’ practice 30.33 76.3 48.7 7.85
Sunhemp incorporation 28 46.77 18.3 26.62
Tied ridges 31.5 65.44 41.2 17.03


G. Subba Reddy, H.P.Singh, Christine King and Sreenath Dixit

 Central Research Institute for Dryland Agriculture

Santoshnagar, Hyderabad 500 059


Ms. Christine King is with the Department of Primary Industries, Queensland, Australia













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