Dams, Displacement, and the Delusion of Development. Allen F. Isaacman
rich delta and coastal estuary regions205 had coevolved, in the predam period, with a very particular flood regime connected to the bimodal pattern of annual rainfall.206
Under normal climatic conditions, Zambezi flow patterns were fairly predictable. Flooding occurred in two stages after the onset of the rainy season, in late November or December. A week or two later, flow rates began to increase, creating small peaks in response to local rainfall runoffs in the lower Zambezi basin. While flows in December could reach as high as 6,740 cubic meters per second, the principal flood normally began in January and peaked between late February and late March (see fig. 2.1). During this period, the river swelled to several times its normal size, overflowing its banks virtually every year between 1930 and 1958—the period for which records of the flow rate exist.207The floodwaters began to recede in April, leaving behind a rich deposit of organic and inorganic nutrients on the lowlands adjacent to the river. During the dry season, from late April through October, water levels diminished rapidly, until the river’s flow returned to its average low point of approximately 400 cubic meters per second. The flooding cycle began anew with the onset of the next rainy season.
The magnitude and duration of the seasonal floods varied over time and from one zone to another. For the forty years preceding Cahora Bassa’s construction, the maximum annual peak flow ranged from five to twenty thousand cubic meters per second , although the extremes were infrequent—occurring only twice.208Even at the lower end, however, the runoff was sufficient to inundate the plains and deposit valuable silt. Table 2.1 documents the maximum flood levels measured at two locations on the lower Zambezi before the construction of Kariba and Cahora Bassa. Mutarara is located about 150 kilometers downriver from the Cahora Bassa gorge, and Marromeu sits in the delta. Despite the annual variability of flood levels, at both sites they were always sufficient to overflow the river’s banks and inundate alluvial fields.
The Zambezi’s annual flooding critically affected the topography and natural-resource base of both the valley and the vast wetlands of the delta. The seasonal runoff ensured high groundwater levels throughout the region and fed channels, tributaries, and lakes—most dramatically in the delta, where it formed a wide riverine landscape with “open mosaics of marsh, pond, oxbows and shallow wetlands.”209During the rainy months of December through March, the width of the inundated floodplains varied from place to place. Carlos Churo of Chicoa Velha, for instance, remembered stretches of the river where floodwaters stretched for seven to nine kilometers on both banks.210In parts of the delta where the alluvial plains were much larger, the floodwaters could span twenty to thirty kilometers.211Some lowland areas, such as the northern floodplains near the confluence of the Zambezi and Shire Rivers, had a spillover that nourished more than eighty thousand hectares of land, while, in nearby Inhangoma, the Zambezi inundated fifty-five thousand choice hectares.212Many of the islands dotting the river also benefited from this extensive seasonal irrigation, as did lowlands adjacent to both the Zambezi’s tributaries and streams flowing into it.
These alluvial lowlands, particularly in the delta, contained some of Mozambique’s most biologically diverse ecosystems. For this reason, the delta itself has long been vital to Mozambique’s national economy and is a wetland of international significance.213A massive eighteen-thousand-square-kilometer zone of flooding and silt deposition, it stretches almost three hundred kilometers along the Mozambique coastline and 160 kilometers inland to the Zambezi’s confluence with the Shire River. For millennia its vast seasonally flooded grasslands supported a wide variety of birds, mammals, and reptiles, while the floodplains themselves were spawning grounds for riverine and anadromous fish and provided dry-season grazing for wildlife.214Coastal estuaries and mangrove forests, central elements of the delta and estuarine environment, were also a fertile breeding ground for shrimp.215The Zambezi flood flows played an extremely important role in maintaining the delicate biochemistry of this unique ecosystem—the pulsing floodwaters during the rainy season flushed accumulated salt from the coastal floodplains, helping to ensure the proper balance between tidal saltwater and riverine freshwater.
For the human residents of the lower Zambezi valley, however, the most valuable effect of the annual flooding cycle was the supply of life-sustaining nutrients deposited along the alluvial plains as the floodwaters receded every April, which, for centuries, supported farming communities and aquatic ecosystems. The annual replenishment of nutrients from the flooding Zambezi was responsible for the rich dark soils (known in local languages as makande, ndrongo, or matope) of the river-fed plains, whose high moisture retention and rich mineral content made them the most desirable agricultural sites in the region. Like fish, wildlife, and other elements of the Zambezi ecosystem, which depended for their survival on the regularity of the natural flow regime, peasant households historically relied on the annual inundation of the floodplains for the very basics of life—fertile soil for growing food crops, dry-season pasture for livestock, and habitats that produced abundant supplies of fish and game. For all these reasons, before Cahora Bassa’s construction, flooding was considered a normal, welcome phase of the agricultural year, around which riverine communities planned their food supply and other household routines, rather than a destructive or traumatic event. “The water used to flood once a year,” recalled José Jone. “People moved to the murumucheias [higher lands] until the waters disappeared. Then we returned home.”216This seasonal pattern of flooding underpinned the organization and viability of a “diversified production system that incorporated flood recession agriculture, livestock management, fishing, gathering and hunting,”217all of which were essential for the food security of peasant households throughout the lower Zambezi valley.
At times, however, the river was also an extremely destructive force—a fact generally not stressed in the oral narratives. The earliest report of flooding in the Zambezi delta was in the mid-1500s, and extreme flooding occurred periodically over the next three centuries.218In the twentieth century there were reports of twenty-one large floods,219and hydrological data collected between 1925 and 1955—a period about which most elders would have heard—at Mutarara, on the northern bank of the Zambezi River opposite Sena, and at Marromeu, further downriver in the delta, indicate nine seasons of extreme flooding provoked by heavy rains before the construction of Cahora Bassa (see table 2.1). Richard Beilfuss and David dos Santos describe the catastrophic flooding in the delta in the mid-twentieth century:
In 1939, the delta reached its highest water levels in recorded history . . . , overtopp[ing] the dikes that were built in 1926 to protect the sugar estates at Marromeu and Luabo, and inundat[ing] most of the 1.2 million ha. delta. The dikes were overtopped again in 1940 and 1944, during what was probably the wettest period in the twentieth century. The most prolonged flooding on record occurred in 1952 . . . , caus[ing] extensive damage to houses and crops on the delta plains. . . . For the fourth time since 1926, the dikes protecting Marromeu and Luabo were overtopped. . . . In 1958, . . . the delta again experienced extreme flooding. . . . Water levels in the delta reached near-record levels, and exceeded catastrophic flood levels for 26 days. Large numbers of Cape buffalo and waterbuck were purportedly drowned by these large floods.220Since the delta’s flooding was due to heavy rainfall and runoff upriver, the destructive flooding of the river during these years necessarily would have adversely affected those living and farming in the Tete-Sena area.
Recession Agriculture in the Floodplain
Everywhere, those interviewed agreed that the floodplain’s rich, dark soil made it the most sought after and densely populated agricultural zone in the region.221One elder described the fertility of riparian land in almost magical terms: “We used to just have to drop a seed in to the soil here and it would grow into a tree.”222Beatriz Maquina, an elderly woman who had farmed in the Chipalapala region her entire life, stressed the agricultural significance of the rich alluvial soils: “Makande land located near the banks of the river always gave us good production. We cultivated a great deal of sorghum as well as some maize.”223Joaquim Sacatucua of Caia echoed her view: “We call the soil ndrongo. It is very fertile, which is why so many people settled here. Because of the rich land we had food, even when the rains did not come.”224Writing in the mid-1960s, a Portuguese planner working