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According to the IPCC Fifth Assess- ment Report (2014), warming over land across the Zambezi Basin and the rest of the continent has increased during the last 50 to 100 years. Data from 1950 onwards suggests that cli- mate change has changed the magni- tude and frequency of some extreme weather events in the Basin. The health, livelihoods and food security of people in the Basin have been af- fected by climate change.

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Lesolle, D., SADC Policy Paper on Climate Change: Assessing the Policy Options for SADC Member States, 2012

Figure 5.4 Rainfall Determining Systems for the

Zambezi River Basin

Figure 5.5 Impact of ENSO on Rainfall in the

Observed Changes in Temperature

Southern Africa including the Zambezi Basin has had a warming trend over the past few decades. This is consistent with the global trend of temperature rise in the 1970s, 1980s and 1990s. Instrument ob- servations from several SADC member states show an increase in temperatures, especially the minimum temperatures.

The observed trend in some southern African countries between 1960 and 2006 indicates an increase in mean annual tem- perature, as shown in Table 5.1. For ex- ample, in Angola the mean annual temperature has increased at an average rate of 0.33o_{C per decade, while in Malawi} the average rate of increase was 0.21o_C per decade in the same period (SADC RCCP 2010). The same report notes that the average annual tem- perature for Angola is projected to increase by 1.5o_{C by 2030, 2.7}o_{C by} 2060 and 3.6o_{C by 2090. This up-} ward trend is projected for all the five countries studied.

Other studies say that Botswana had an increase in warming at a rate of 0.017°C per year between 1910 and 2000 (Lesolle 2012). See Figure 5.6.

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Red line shows actual data for 1910 to 2000. Projection is based on the IS92a IPCC climate change scenario.

Lesolle, D., SADC Policy Paper on Climate Change: Assessing the Policy Options for SADC Member States, 2012

Figure 5.6 Changes in Minimum Temperature for Gaborone, Botswana

Meteorological Services of Zimbabwe, 2009

Figure 5.7 Annual Mean Temperature Changes for Kariba

Young and others, 2010

Table 5.1 Observed and

Predicted Temperature Changes

Country Angola Malawi Mozambique Tanzania Zambia Change in o_C per decade 1960-2006 0.33 0.21 0.13 0.23 0.29 2030 1.5 1.3 1.2 1.3 1.5 Projected changes in o_C 2060 2.7 2.5 2.3 2.3 2.6

For Mozambique, the mean annual temperature increased by 0.6°C between 1960 and 2006, with an average rate of 0.13°C per decade (INGC 2009). Other noticeable changes in temperature are in Namibia. Between 1950 and 2000, the country experienced warming at a rate of 0.023°C per year. It is predicted with a high degree of certainty that Namibia will become hotter throughout the year, with a predicted increase in temperatures of between 1°C and 3.5°C in summer and 1°C to 4°C in winter in the period 2046 - 2065. Maximum temperatures have been getting hotter over the past 40 years, as observed in the frequency of days ex- ceeding 35°C. Equally, the frequency of days with temperatures below 5°C has been getting less, suggesting an overall warming (Government of Namibia 2011). For Zimbabwe, a rise in tempera- ture is noted at Kariba where mean an-

nual temperature rose from 26.3o_{C in} 1970 to 29.1o_{C in 2008 (SARDC and} HBS 2010). See Figure 5.7.

The trend shows an increase in the number of warm spells and a decrease in the extreme cold days in southern Africa between 1960 and 2006 (Boko and others 2007). As shown in Table 5.2, the ob- served frequency of hot days per decade between 1960 and 2006 has been increas- ing ranging from 0.61 percent per decade for Tanzania to 3.11 percent per decade for Angola. For cold days the frequency is showing a decrease, with Angola de- creasing by 4.9 percent per decade while Malawi decreased by 1.01 percent per decade in the same period.

Projected trends for the five coun- tries studied shows continuous increase in frequency of hot days with Mozam- bique showing a 28 percent increase by 2060 and 42 percent by 2090. A similar trend is projected for the other countries (see Table 5.2).

The increase in temperatures is ex- pected to continue even if the green- house gas emissions were to be stopped today. The temperatures in the region are expected to warm by between 1.0°C and 3.0°C by 2080 (IPCC 2014).

This means the Zambezi River Basin will continue to experience warmer tem- peratures. As a result, the agricultural sea- sons may change and planting times could vary for different crops. The Basin area could attract more pests, and malaria could spread to places where it is not en- demic. Hotter temperatures could mean heat stress and changes in natural ecosys- tems. This can change the productivity of the rangeland, grazing, and food produc- tion. There will be challenges for agricul- ture, water, health and other key socio-economic sectors if they do not adapt to these changes.

Observed Changes in Rainfall Characteristics

The changes in rainfall are best ex- pressed as changes in intensity, extreme rainfall events (storms) and changes in the rainfall season (onset, cessation and

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Young and others, 2010; SADC RCCP, 2010

Table 5.2 OObserved and Projected Changes in Frequency

of Hot and Cold Days

Country Angola Malawi Mozambique Tanzania Zambia Observed change in frequency per decade between 1960-2006 (%) Hot days 3.11 1.94 1.58 0.61 2.73 Cold days -4.9 -1.01 -0.9 0.03 -1.4 Hot days 30 22 28 27 22 Cold days 1 2 2 2 2 Projected changes in

frequency of hot and cold days % Frequency 2060 % Frequency 2090 Hot days 40 31 42 40 31 Cold days 0 0 1 0 1

length). Overall, since 1950, the coun- tries in the Zambezi Basin have wit- nessed a downward trend in rainfall. This is in line with the findings of the IPCC Fifth Assessment Report (2014) which indicates that rainfall years iden- tified as “below normal” are becoming more and more frequent.

Among the most notable climate changes predicted to occur are a de- crease in rainfall across the Basin, which is estimated at 10–15 percent. Also predicted is an estimated decrease in run-off and significant changes in the seasonal pattern of rainfall across the Basin, including delayed onsets, as well as shorter and more intense rain- fall events, implying an increase of fre- quency in floods and droughts (SARDC and HBS 2010; Beilfuss 2012). The beginning of the rain sea- son is becoming less predictable. Heavy rain events are more frequent and intense but episodes of drought occur as well. In Botswana, rainfall is expected to decrease by a significant amount as shown in Figure 5.8.

Heavier rainfall will result in an in- creased incidence of flooding in many areas. Reduced runoff aggravates exist- ing water stress, reduces land quality, lowers quantity of water available for

domestic and industrial use, and limits hydropower production.

In the Zambezi Basin region in Mozambique, the rainfall varies consider- ably within annual cycles with 60-80 per- cent of the annual precipitation falling in the period from December to March. The mean annual rainfall has decreased at an average rate of 2.5mm per month per decade, or 3.1 percent between 1960 and 2006. This annual decrease is largely due to a reduction in December, January and February rainfall, which has decreased by 6.3 mm per month, or 3.4 percent per decade (INGC 2009). See Figure 5.9.

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Actual data for 1910 to 2000 and projection based on the IS92a IPCC climate change scenarios for the period up to 2080.

Lesolle, D., SADC Policy Paper on Climate Change: Assessing the Policy Options for SADC Member States, 2012

Figure 5.8 Actual and Predicted Future Rainfall in Gaborone, Botswana

INGC, 2009

Figure 5.9 Decrease in Water Availability June-December

The unpredictable beginning of rain season and the decrease of rainfall dur- ing December-February, which is the peak crop season in Mozambique, has significant implications on the agricul- tural sector which is mainly rain-fed and practiced by smallscale, subsistence farmers. This high variability in rainfall (Fig 5.10) leads to recurrent floods and droughts with heavy impacts on agricul- tural sectors, roads and rural livelihoods in general. The coping capacity of the communities is low therefore most of extreme events associated with climate variability become a disaster risk in many parts of the Zambezi valley.

Despite a late start to the season, most of southern Africa received heavy rains from December 2011 into 2012, resulting in flooding in several countries. Tropical Cyclone Favio came ashore on

the coast of Mozambique on the morn- ing of 22 February 2007 and as it trav- elled further inland, the storm brought heavy rains to Zimbabwe (SANF 2012).

Observed and Predicted Changes in Sea Level

While the melting of continental ice sheets results in a rise in sea levels, the primary contributor is thermal expan- sion due to increasing temperatures, and this is well quantified. According to the 5th_{IPCC assessment report (2014), over} the period 1901-2010 the global mean sea level rose by 19 centimetres and will continue to rise during the 21th century. The high scenario shows a rise of 10mm by 2030, 100mm by 2060 and 500mm by 2100 (IPCC 2007 in SARDC and HBS 2010). This can cause perma- nent flooding of the sea coasts, estuaries and deltas including the Zambezi Delta. Sea level rise will present a threat to the basin through salt water intrusion. In the Zambezi Delta more than 240 sq km of land could be impacted with in- land saltwater penetration of about 28km by 2030 (Brundrit and Mavume 2009). Drinking water supplies for coastal communities will be affected, thus increasing the burden of women who will have to fetch water from afar, unless modern methods are put in place for sustainable access to clean piped water. Coastal infrastructure such as roads and buildings will be at risk of damage.

Marshland vegetation in the delta could provide some natural resistance to the intrusion. High flows from annual flooding of the Zambezi River could help to wash back some of the salt water. Conservation measures of the marshland vegetation and eco-hydraulic management of the Cahora Bassa reser- voir releases are required to ensure that these restorative processes occur.

Observed Changes in

Climate Related Extreme Events

Frequency and severity of droughts, floods and cyclones have increased in the

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INGC, 2009

Figure 5.10 Rainfall Anomalies Across Central Mozambique

where Zambezi Basin is Located

Zambezi Basin since the 1950s. Between 1988 and 1992 the sub-region experi- enced more than 15 drought events (Boko 2007). Some notable droughts and floods are shown in Table 5.3 below.

Map 5.1 shows that dry periods have been frequent in the northern parts of the basin in Angola and Zambia be- tween 1995 and 2013, and also in Malawi and northern Mozambique.

Map 5.1 shows that for the past 18 years most of the basin has witnessed below average rainfall at least once dur- ing the first quarter of the year. The Basin is expected to face drier and more

prolonged drought periods. According to several studies cited by the Intergov- ernmental Panel on Climate Change, rainfall is expected to decrease by 10-15 percent over the Basin during the next century (Beilfuss 2012).

As a result, a significant reduction in the amount of water flowing through the river system is expected and this affects all eight basin countries. The water that feeds the Zambezi River is expected to decrease by between 26 and 40 percent in another four decades, the study revealed. High evaporation rates have reduced the level of water reservoirs in most parts

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Table 5.3 OOccurrence of Extreme Events in the Zambezi Basin

2014-2015 2012-2013 2008-2009 2007 2005-2006 2004-2005 2001-2003 1999-2000 1994-1995 1991-1992 1986 – 1987 1983 1982 1981 – 1982 1967 – 1973

Tens of thousands of people in Malawi, Mozambique and Zimbabwe have been severely affected by floods caused by Tropical Storm Chedza, which started in December and continued through February 2015. Malawi has been hard hit by the current floods. More than 200 people have died and 500,000 people displaced. In Mozambique more than 150,000 people have been affected and about 6,000 in Zimbabwe.

Following poor performance in November, good rains were received in the first 10 days of December but dry conditions resumed late January through to May in the southern parts of the Zambezi Basin. The basin experienced flooding, which displaced thousands of people in Angola, Botswana, Malawi, Namibia and Zambia.

Floods induced by Cyclone Favio impacted on Mozambique and parts of Zimbabwe.

Parts of southern Africa received very heavy rains resulting in flooding that caused considerable infrastructural damage, destroying schools, crops, roads and telecommunications.

Many parts of the Zambezi Basin received below-normal rainfall during the agricultural season. Several riparian states declared national disasters.

Severe drought in the SADC region.

Cyclone Eline hit the region and widespread floods devastated large parts of the Limpopo basin (southern and central Mozambique, southern-eastern Mozambique, parts of South Africa, Botswana and Zimbabwe). In Mozambique alone this affected 2 million people with 650,000 forced to abandon their homes.

Many countries in the SADC region were hit by a severe drought, surpassing the impact of the 1991- 1992 droughts.

Worst drought in living memory experienced in southern Africa, excluding Namibia. Drought conditions returned to the region.

This year saw a particularly severe drought for the entire African continent. Most of sub-tropical Africa experienced drought.

Severe drought occurred in most parts of southern Africa.

This six-year period was dry across the entire region. Some records show a severe drought.

ZAMCOM, SADC and SARDC 2015, updated from SADC/SARDC and others, Southern Africa Environment Outlook, 2008; SADC/SARDC and others, Zambezi River Basin Atlas of the Changing Environment, 2012; and SADC-FANR 2013.

of the Basin, including the Kariba and Cahora Bassa dams.

When the rains do fall, this will be more intense, triggering extreme flood events. Recent floods and their impact on the existing dams offer a possible view of future challenges. In 2007, heavy rains over the Zambezi basin threatened the dam structure, forcing authorities to open the sluice gates of the Cahora Bassa Dam, affecting up to half a million people, some displaced and others had their crops destroyed.

In a case study on the floods and cy- clones that struck Mozambique in 2000, the Overseas Development Institute warned that Cahora Bassa and Kariba, which are the biggest dams on the Zam- bezi River, do not have the spillway ca- pacity to cope with the very large floods that occur on the river every 5-10 years (Beilfuss 2012).

Contrary to the expected droughts in parts of Botswana, Namibia and Zim- babwe, Mozambique was dealing with heavy rains and cyclones that frequently hit the country. The consequence is fast- rising river levels causing more harmful floods to farmers and their valuable farmland along the lower Zambezi shores.

With its long coastline and about 40 percent of its population living and working in coastal districts, Mozam- bique is particularly vulnerable to trop- ical storms. The results are already visible with serious erosion destroying local infrastructure and farmland.

Some parts of the Zambezi River Delta frequently report alternating droughts and floods over the past two decades. A study by Brida and Sokona (2013) reported that during the first part of the century, Mozambique was domi-

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SADC/SARDC and others 2012

nated by flooding, particularly the 2000/01 season, followed by a period of drought with a peak in 2005 (see Figure 5.11 below).

Other observed changes are in the frequency of tropical cyclones. The tropical cyclone season for the South West Indian Ocean is from November through April, with the highest fre- quency of occurrence expected in Jan- uary and February. The presence of cyclones in the region leads to extensive flooding, resulting in economic losses and destruction of infrastructure, crops and livelihoods. The future looks similar as observed data shows an increase in the cyclone activity (Table 5.4).

Key Risks Predicted for the Zambezi River Basin over the Next Century

• The Zambezi Basin can expect a significant warming trend of 0.3 - 0.6°C.

• Temperature increases across the Basin will increase open-water evaporation.

• Multiple studies cited by IPCC estimate that rainfall across the basin will decrease by 10–15 per- cent.

• Significant changes in the sea- sonal pattern of rainfall across the Basin are predicted, including delayed onsets, with shorter and more intense rain- fall events.

• All Zambezi Basin countries will experience a significant reduction in average annual stream flow. • Multiple studies estimate that the

Zambezi runoff will decrease by 26–40 percent by 2050.

• Increasing water stress is a seri- ous concern in the semi-arid parts of the Zambezi Basin (Beilfuss 2010).

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Brida and others, 2013

Figure 5.11 Flood and Drought Events in the Zambezi River Basin - Mozambique Case

www.wmo.int

Table 5.4 Changes in Activity of Cyclones in Categories 4 and 5 for the

South West Indian Ocean Basin

Basin

South West Indian

Period

1975–1989 1990–2004

Number Percentage Number Percentage 23 18 50 34

Impacts of Climate Change in the