Home | The Basin | The River Basin | Climate and Weather | Climate Change

Climate Change

There is growing consensus among scientists and politicians that the global climate is changing. The main impact of these changes on humans and the environment is the availability and quality of water and increased exposure to weather-related natural disasters (World Water Assessment Programme 2009). Not only can climate change directly reduce the availability of water, but it can also have indirect impacts on other issues such as food security, loss of biodiversity and increased prevalence of disease.

These changes to the global climate system and the subsequent regional and sub-regional impacts are believed to be incited by anthropogenic (man-made) emissions of greenhouse gases (GHGs). The primary GHGs are carbon dioxide, methane, sulphur dioxide and nitrous oxide (IPCC 2008). Increases in population and development since the industrial revolution have lead to increases in atmospheric concentrations of GHGs, as demonstrated by research using ice-core drilling. Records developed from ice-cores dating back 10 000 years have been combined with more recent data collected since 1 750 to compare increases in GHGs to background levels.

The climate changes reflect a general increase in global temperature and changes to the composition of the atmosphere, which in turn cause changes in precipitation, temperature and other atmospheric and weather-related patterns. The ultimate result is ongoing change in catchment rainfall-runoff processes and the availability of water, which will have a profound effect on ecosystems and the communities that rely upon them.

Farmers and Climate Forecasts, Zimbabwe

In Zimbabwe, only 3 percent of farmers use climate information for planning purposes. Some of the reasons given are that the information is not received in time and that farmers do not trust the meteorological information. Although farmers listen to climate forecast from radios, the poor and marginalised farmers prefer to use their traditional knowledge systems as a control. When contemporary climate forecasting deviates from traditional forecasts, the farmers’ inclination is towards indigenous information for reasons that it blends well with the culture, has been tried and tested over the years, and is in a language that the farmers understand.

There is often a striking similarity between indigenous and contemporary climate indicators. Some indicators are the same in both systems, such as wind direction, clouds and temperature. In addition, indigenous climate predictions are also based on plant and animal behaviour.

Farmers associate heavy production of tree leaves with a good season while high fruit production is a sign of a poor season. The reasoning behind this observation is that high fruit production implies that people will be living on fruits for lack of alternative foods. The production of white flowers by a local tree called mukuu is also a signal for a dry season, while flower production on top branches of a tree called mukonde indicates a good rainy season. Other indigenous signs of an imminent drought include: heavy infestation of most tree species by caterpillars during springtime; late bearing and lack of figs in July-September of a tree called mukute; late maturing of acacia trees along valleys; and drying off of chigamngacha fruit between September and early November.

One of the most important animal indicators is the behaviour of spiders. When spiders close their nests, an early onset of rain is expected because spiders do not like any moisture in their nests. When a lot of crickets are observed on the ground, a poor rainy season is expected. The movement of elephants is associated with occurrence of rainfall because they need a lot of water. A stork flying at very high altitude is associated with a good season. Observing a bird singing while facing downwards from the top a tree is a good indicator that it is about to rain, while a lot of birds is a sign of heavy rain.

The wind blowing from west to east, and from north to south, is assumed to bring a lot of moisture and a good rainy season. The prevalence of a strong wind from east to west during the day and at night between July and early November is an indicator of drought.

Source: FAO 2004

A recent study completed by Zhu and Ringler (2010) modelled current and future water resource scenarios for the Limpopo River basin up to 2030. The model used was a semi-distributed hydrological model in combination with the Water Simulation Module of the International Model for Policy Analysis of AgriculturalCommodities and Trade (IMPACT). Input data from four IPCC SRES scenario outputs (A1FI, A2a, B1a and B2a) were used to develop the model output scenarios, which used mean monthly temperature and precipitation values from 1961 – 1990 as a baseline.

The current assessment of water availability showed that given no further change in climate and water infrastructure in the basin, the current resource availability situation in the basin is already stressed. However, but with appropriate management interventions, the situation could be stabilised over the coming years. When the climate changed-based model scenarios were utilised, using projected climate change impacts (temperature and precipitation) and increased water utilisation for irrigation, the models showed that water scarcity would increase.

While water scarcity is predicted to increase in many parts of the world, arid and semi-arid regions such as the Limpopo River basin, will suffer the most. These scenarios, if realised, will likely impact availability of water for domestic and agricultural use, creating water shortages and reduced agricultural productivity.

To access a copy of the scientific paper published with this study, please refer to the Document Library.

Current ongoing initiatives.

LIMCOM's current ongoing interventions being undertaken

CURRENT ONGOING INITIATIVES

Work With Us

News

Publications

Climate Change

Farmers and Climate Forecasts, Zimbabwe

Current ongoing initiatives.

Our Work