Adaptation of rainwater management practices

Since climate change will result in increased frequencies of extreme events (droughts, cyclones, floods), and higher rainfall variability in terms of time, space and amounts, a potential adaptation measure would be to se-cure water availability for crop and livestock production.

One way of doing this is to harvest rainwater and runoff. At a first glance, inadequate water supply is a major challenge to agro-pastoral systems.

However, studies show that the rains provide adequate water quantities for crop production but the water becomes lost through run-off, evaporation from bare soils and deep percolation beyond the rooting zone of annual crops (Pasternak et al. citing Fox / Rockstrom 2003). WOCAT (2007) notes that in the drylands rainwater is lost through seasonal surface run-off in the order of 15–20 percent and another additional 40–70 percent is lost through evaporation from soil surface leaving less than half of the rainfall available for crop and fodder production. In the following, the various ways that smallholders harvest rainfall are analysed.

While water is available (rainfall, flowing streams and rivers) during the rainy season, it becomes scarce during the dry seasons making people (especially women and children) walk long distances in search of water for domestic uses. In many dry regions of SSA (for example, Kenya, Tanzania, Ethiopia, and Namibia) people dig holes in the sand beds of streams and rivers to fetch water. This traditional practice has been en-hanced by building sand dams – a concrete wall at strategic sites across the channel that sometimes serve as a bridge. Sand dams trap sand during flooding thereby blocking extra sub-surface water in the sand bed and thus increase available water for harvesting in dry times (Ifejika Speranza 2006b).

Sand dams have the benefits to improve water infiltration, provide drink-ing water for people and livestock, and control erosion. It also contributes to regenerating the environment as vegetation prospers in such sites thereby attracting other biological resources. Sand dams are estimated to be costly in terms of mobilising people to participate and labour intensive.

Constructing sand dams depends on external financial support to purchase the materials needed for construction and often communities have to be mobilised by external agents (extension officers, NGOs, church

organisa-building sand dams. Since the benefits are community-wide, ownership by the community is rapidly achieved. However, it is also culturally accept-able and in many cases a major source of water in the areas where it is used (ibid). Thus, the pressure on external dependence for inputs may compromise this adaptation practice. In order to improve resilience to climate change, communities need to be sensitized to maintaining the sand dams. Although they are long-lasting, some sand dams may require stabili-sation and repairs due to flood damages. Thus, forming community groups in charge of maintaining the sand dams is a promising way to maintain resilience.

Micro-catchments water harvesting techniques (contour bunds) are used for planting crops and trees. An example of such micro-catchment method is the trus cultivation, that is, a traditional water conserving method of cultivation used on clay soils that harvests surface run-off by constructing low earth bunds called trus (Port Sudan: Osman-Elasha et al. 2006). Ac-cording to Osman-Elasha et al. (2006), indigenous trus cultivation has gained in importance in recent years, as rain-fed farming on sandy soils became increasingly risky and people became unable to produce enough food for consumption. As a result of the good crops of sorghum from trus cultivation, Osman-Elasha et al. (2006) report that more farmers started to shift to clay soils and practice trus cultivation. Magun cultivation was adopted in response to sand encroachment on top of fertile soil, whereby holes of 10–30 cm in diameter and 5–15 cm deep, spaced at distances of 40–70 cm, are dug to plant seedlings of tobacco and water melon (Osman-Elasha et al. 2006).

Rainwater harvesting for crop and livestock production is an old farm management technology that is being re-examined due to its potential to address climate change impacts through stabilising on-farm water supply.

Where they are practiced, farmers dig pans to harvest run-off, thereby stabilising on-farm water availability. The water harvested in such pans can sustain farm production through dry spells, dry seasons and seasons affected by droughts. However, despite its production and economic bene-fits, this practice of harvesting rain-water for crop and livestock produc-tion has not been widely adopted in the drylands. Hence rain water har-vesting for crop production is being revisited by various research teams to examine why the technology has not been adopted widely despite the success of the few farmers that practise it.

Table 7: A resilience check at farm-level: Assessing the contributions of rain water harvesting to resilience of smallholder agriculture to climate variability and change

Components of Resilience Indicators Resilience check Ecological Economic Social

In what ways and how much does the adaptation … Spheres of

action

Increase livelihoods activity options?

VH VH VH

Human capital

Promote human capi-tal (endowments)?

VH VH L

Access (rights)

Promote entitlements (access)?

NA NA NA

Income Improve incomes? NA VH NA

Climate protection

Promote climate protection?

N N N

Buffer capacity (robustness to uncertainty)

Site-specific knowledge

Require or use site-specific knowledge?

VH N N

Source: Based on literature / own design

Legend: NA: Not Applicable; N: None; VL: Very Low; L: Low; M: Moderate;

H: High; VH: Very High

Table 7 continued

Components of Resilience Indicators Resilience check Ecological Economic Social

Incentives In what ways and how much do policies promote (at least not hinder) the adaptation option (incentives)?

H H NA

Diversity In what ways and how much does the adaptation promote diversification or diversity?

VH VH VH

Stewardship In what ways and how much is the adaptation geared towards stewardship (in contrast to ex-ploitation/mining resources) rather than just manage-ment?

M NA NA

Buffer capacity (robustness to uncertainty)

Environmental protection

In what ways and how much does the adaptation practice benefit the environ-ment?

M NA NA

Source: Based on literature / own design

Legend: NA: Not Applicable; N: None; VL: Very Low; L: Low; M: Moderate;

H: High; VH: Very High

Table 7 continued

Components of Resilience Indicators Resilience check Ecological Economic Social

Local much does the farmer rely on own resources in practicing the much does the farmer rely on own knowl-edge in practicing the adaptation?

H L L

Self-organisation

Flexibility In what ways and how much does the farmer have the freedom to decide?

H H L

Source: Based on literature / own design

Legend: NA: Not Applicable; N: None; VL: Very Low; L: Low; M: Moderate;

H: High; VH: Very High

Table 7 continued

Components of Resilience Indicators Resilience check Ecological Economic Social

Adaptive capacity

Source: Based on literature / own design

Legend: NA: Not Applicable; N: None; VL: Very Low; L: Low; M: Moderate;

H: High; VH: Very High

Table 7 continued

Components of Resilience Indicators Resilience check Ecological Economic Social

Feedback

Source: Based on literature / own design

Legend: NA: Not Applicable; N: None; VL: Very Low; L: Low; M: Moderate;

Table 7 continued

Components of Resilience Indicators Resilience check Ecological Economic Social

Gender Gender positive / negative

In what ways and how much does the adaptation reduce existing gender inequalities?

NA M H

Source: Based on literature / own design

Legend: NA: Not Applicable; N: None; VL: Very Low; L: Low; M: Moderate;

H: High; VH: Very High

A resilience check in Table 7 shows the various ways that rain water har-vesting (RWH) for crop and livestock production builds the resilience of communities to cope with and adapt to climate change.

Contributions of rainwater harvesting to resilience to climate change:

Contribution to ecological resilience

– Through harvesting rainwater, the destructive effects of runoff are reduced, thereby contributing to environmental protection. Reduced soil erosion means that the silt-load of rivers is reduced, thereby enhancing river flow, protecting river fauna and helping keep the costs of water purification for urban consumers low.

– Because of the harvested water, the range of crops that can be grown is expanded, thereby contributing to the diversity of the cropping system, and by extension to resilience.

– Research and extension tend to focus on progressive farmers to understand why one farmer succeeds against odds to derive beneficial outcomes while other farmers do not. Hence the feedback between such actor categories and the farmer is high. Through this feedback and practice the farmer increases his/her knowledge of the environment and

adapts his/her management accordingly, thus indirectly contributing to ecological resilience.

Contribution to economic resilience

– Harvesting rainwater for crop and livestock production increases the buffer capacity of smallholders to deal with climate change. By har-vesting rainwater, the farmer increases the on-farm livelihood options – collected water can be used for growing crops through irrigation during dry spells, dry seasons and droughts. Thus farm production is de-coupled from direct dependence on rainfall which will become more variable with climate change. The water pan can also serve as a fish pond thereby diversifying farm livelihoods and consuming the mosquito larvae which usually populate such ponds. By having crops to sell when other farmlands are dry and bare, the farmer increases own incomes and can maintain this source of income over time. Through adopting technologies like irrigation the farmer improves own human capital as he/she learns through practice. By recognising the value of water as a resource, such farmers are more likely to improve the efficiency of resource (water) use with time by adopting such technologies as drip irrigation.

– Rainwater Harvesting (RWH) depends highly on local (rain-water/runoff) and farm resources (labour). The farmer can phase the establishment of a RWH-system by starting small and successively expanding to the desired capacity. The farmer does not require a high level of knowledge for this practice but learns through experience.

Thus, considering that farm labour is likely to be adequate in most cases to start this adaptation, the farmer has a high level of freedom to decide and self-organise.

– The practice of RWH increases adaptive capacity as the farmer is continuously learning and improving the RWH system. Through achieving food security and earning additional incomes, the practise of RWH reduces power differentials between the adopters and wealthier farmers. However, it also has the potential to increase the power differentials between adopters and their peers, which can reduce the social capital of the farmer among his/her peers.

– The economic cost-benefit ratio is high. Initially, the farmer may have to forfeit other activities in order to invest more time to establish the RWH infrastructure (pan, pipes and drip-irrigation infrastructure).

– The ability of RWH to reduce gender inequalities in an economic context varies widely according to household organisation. In cases where it is the wife that sells farm produce to community members, it increases women’s access to cash. It also increases access to food and reduces the time women and girls have to spend to fetch water from distant streams and rivers.

Contribution to social resilience

– The contributions of rainwater harvesting to social resilience are diverging. Through practicing RWH, the farmer becomes a node of knowledge that is potentially of interest to other actors in agriculture.

However, non-adopters can perceive the farmer as behaving out of the norm and may reduce their contacts with the farmer. This argument is based on ongoing empirical analysis and the fact that RWH remains an island of technology adoption in many SSA regions despite the evidence that its adoption increases livelihood security. So answers must be sought to the question of why slow diffusion and limited adoption of farm technologies persist in many areas. Nevertheless, against the losses in social capital there are also gains in social capital as the farmer becomes a source where other villagers come to borrow food.

Im Dokument Resilient adaptation to climate change in African agriculture (Seite 127-136)