Managing scarce water resources for agricultural production in the Caribbean

By Leslie A. Simpson, Stanley Rampair and Greg Marshall | Natural Resources Management Specialist of Caribbean Agricultural Research  and Development Institute, Senior Irrigation Specialist and Agricultural Engineer respectively

Introduction

Caribbean agricultural production is dominated by rain-fed crops that are highly susceptible to drought conditions. The extreme variations of rainfall in the region can have devastating consequences for farmers, their families, and their communities. In 2009/2010, a severe drought caused millions of dollars in lost income in the Caribbean agricultural sector which was worsened by increased bush fires on farms resulting from the hot dry conditions.

Caribbean farmers have therefore become very wary of the risk that drought poses to their livelihoods and have increasingly attempted to increase their on-farm water management efficiency in order to mitigate the risk. This article details two successful cases of improved on-farm water management in the region to stave off the risks of drought.

Managing Drought Risk in Barbados

In Barbados, Mr. Anderson Nicholls owns and cultivates a 22.83 hectare farm in Mount Wilton, St. Thomas. Mount Wilton falls just outside an area known as the Scotland District, which is the highest point of the island at 400 metres above sea level, has soils of volcanic origin that are clayey but with high pH due to calcareous deposits from the volcanic materials and receives the highest amount of annual rainfall with a mean of 2,160 mm. Most of the rain in the region, however, falls only in the wet season from June to December – leaving much of the year prone to drought conditions.

Mr. Nicholls grows sugarcane, plantain, banana and coconut as well as short-term food crops like tomatoes, cabbage, carrots and beans.In the 1980s, he sourced water for his crops from local springs around the farm during the dry seasons. Annually, when these springs ran dry, he transitioned to using expensive, potable, domestic water to irrigate the more highly valued food crops.In the 1990s, a surface pond was built in a watercourse just northwest of the farm. Local springs were cleared so that water could be channelled into the pond; however, the pond had to be abandoned due to continual sedimentation.

In 2004, Mr Nicholls constructed another pond using a heavy duty polyethylene pond liner with an estimated capacity of 17,035 m3. It harvested surface water runoff from upstream areas, and rainwater from the roof of a farm building. Water was channelled into the pond via a 3m x 10m catchment inlet with a boulder filter pack, which reduces the suspended solids in the runoff water before it enters the pond. Sediments that accumulated in the inlet sump were a subsequent benefit of the pond system and were periodically removed and reapplied to the fields.

A total of 2.0 ha are irrigated by this stored water during the dry season. 0.82 ha is drip irrigated (mainly for the tomato crop) and the other crops are sprinkle irrigated. Since the construction of the pond, Mr Nicholls has saved approximately US$4,000 per year in irrigation water cost by not using any potable water. He is also able to have year-round production of food crops, and sustained high yields even under very dry conditions including the drought of 2009 to 2010 when his pond was never dry.

Using Solar Powered Drip Irrigation to Manage Drought in Jamaica

In Jamaica, the Ebanks family has had a long history of over 50 years farming in Flagaman, Southern St. Elizabeth. The area is part of an elevated plateau (approximately 560 m above sea level) consisting of a rolling topography with a red bauxitic soil that is deep and friable and allows for rapid root development but is low in nutrients and fixes elemental Phosphorus. Mean annual rainfall in the area is 1450 mm and as in Barbados this falls mainly in the June to December wet season.

Beginning first with the traditional system of “slash and burn,” the family has gradually developed a reliable water efficient method of food crop production. In the 1960’s water was manually transported from the house tank to the field to fill a 45 gallon (200 litre) drum and then using a watering can applied to the root of every plant in the field. This process was time consuming and laborious.

The process was later enhanced by covering the soil with Guinea grass (Panicum maximum) as mulch, reducing the amount of water required for the crop. But the success of the crop still depended on sourcing and applying water. To supplement the limited water collected from rainfall, truck borne water was bought at high prices. But application was still manual.

In 2003, the government of Jamaica introduced gravity drip irrigation to the community, eliminating the laborious manual application of water. But the cost of water was still prohibitive. This necessitated the construction of a water harvesting and storage system to supply water to the farm. The capital cost was high but this paid for itself in a short time compared to buying trucked water. The system consisted of a 243m3 concrete water tank which was filled from the house roof and a 405 m2 concrete catchment area.

Originally, the water from the concrete tank was pumped to the in-field water tank by diesel pump, but with increasing fuel prices this became prohibitive. In 2009, The Food and Agricultural Organization (FAO) Small Scale Irrigation and Rainwater Harvesting Project chose the Ebanks family to demonstrate the use of solar pumps along with the gravity drip system to improve water management and water use efficiency on the farm. The solar pump provided the energy to move the water from the concrete storage tank to two elevated 4.5 m3 plastic tanks to which a drip irrigation system is connected and which serves approximately 0.2 ha of vegetable cultivation.

These innovations have resulted in a more reliable and sustainable crop production system, higher yields, the more efficient use of water and energy, and a better standard of living for the family. They estimate that with this new system of cultivation yields have increased fourfold in the last 50 years. For example, a cantaloupe plot, which yielded about 12,000kg per hectare less than ten years ago, now produces 38,000kg.  

Conclusions

These two case studies clearly indicate that rain, springs or other available water sources can be successfully harvested for on-farm water storage; and when combined with energy efficient irrigation can contribute to the development of on-farm water management systems which are able to mitigate the risk of drought to small farmers in the Caribbean.