Water scarcity and abundance, water productivity and their relation to poverty - Water Scarcity, Livelihoods and Food Security - page 23

farming systems and capture fisheries in water-rich basins such as the
Mekong are adapted to seasonal flooding. According to the timing and
extent of the floods, however, they may destroy wet season crops, or they
may enable wet- or dry-season cropping.

The BFPs assembled basic information on annual rainfall, and its seasonality
as measured by the coefficient of variation of monthly rainfall (Table 2.2).
Unreliability can contribute to poverty traps as noted by Grey and Sadoff
(2002, p. 4) regarding Africa:

We have all witnessed . . . catastrophic flood and drought—the endemic
and unpredictable consequence of Africa's hydrological variability. The
economic impacts can be a significant proportion of GDP and social
impacts are incalculable [as is] the suffering of individual families and
communities, as years of labor in land preparation and crop development
is withered by drought or washed away by flood . . . the very existence of
extreme variability itself creates disincentives for investment and affects the
performance and structure of economies, as the unpredictability of rainfall
and runoff encourages risk averse behavior in all years, promoting patterns
of development that can trap economies in a low-level equilibrium. Thus,
even in years of good rains, economic productivity and economic
development can be constrained by conditions of hydrological variability.

In the Limpopo Basin, 80 percent of the annual precipitation falls between
November and late February with a mean of 50 rainy days. Variability in
rainfall, soil type, ground cover, and slope gives erratic runoff and pronounced
seasonal variation in flow, with negligible flow in the dry season. Seasonal
rainfall patterns vary unpredictably and substantially from one year to the next.
(PN62) (Sullivan and Sibanda, 2012). The Volta Basin has more rainfall than

Table 2.2 Annual precipitation and its seasonality in the BFP basins.

Basin Annual total rainfall Precipitation seasonality

mm/yr CoV%

Andes 784 78

Ganges 1073 125

Karkheh 348 89

Limpopo 547 84

Mekong 1713 86

Niger 1017 108

Nile 618 103

São Francisco 975 84

Volta 973 96

Yellow 438 93

Source: Mulligan et al. (2012a).