JPCE 925 No. of Pages 11, DTD = 5.0.1
ARTICLE IN PRESS
17 September 2004 Disk Used
Physics and Chemistry of the Earth xxx (2004) xxx–xxx
www.elsevier.com/locate/pce
2 Evaluation of the impact of climate change on hydrology and
3 water resources in Swaziland: Part I
OF
a,*
4 Jonathan I. Matondo , Graciana Peter a, Kenneth M. Msibi b
a
5 Water Resources Branch, Department of Geography, Environmental Science and Planning, University of Swaziland, Private Bag 4
6 Kwaluseni, Swaziland
PRO
b
7 Water Resources Branch, Swaziland
9 Abstract
10 It has been identified that, long-term climatic changes (Pleistocene ice ages) have been caused by periodic changes in the distri-
11 bution of incoming solar radiation due to the variations in the earthÕs orbital geometry, that is the tilt, precision of equinoxes and
12 eccentricity which take place with periodicity ranging from 41 to 9508 thousand years. However, it has been considered that the
13 major potential mechanism of climate change over the next few hundred years will be anthropogenic green house gas warming
TED
14 up. A number of gases that occur naturally in the atmosphere in small quantities are known as ’’greenhouse gases. Water vapour,
15 carbon dioxide, ozone, methane, and nitrous oxide trap solar energy in much the same way as do the glass panes of a greenhouse or
16 a closed automobile. This natural greenhouse gases effect has kept the earthÕs atmosphere some 30 C hotter, than it would otherwise
17 be, making it possible for humans to exist on earth. Human activities, however, are now raising the concentrations of these gases in
18 the atmosphere and thus increasing their ability to trap energy. The enhanced greenhouse gas effect is expected to cause high tem-
19 perature increase globally (1–3.5 C) and this will lead to an increase in precipitation in some regions while other regions will expe-
20 rience reduced precipitation (±20%). The impact of expected climate change will affect almost all the sectors of the human endeavor.
21 However, the major purpose of this project is to evaluate the impact of climate change on hydrology and water resources and estab-
C
22 lish the appropriate adaptation strategies for Swaziland. The impact of climate change on hydrology and water resources will be
23 evaluated using General Circulation Model results (rainfall, potential evapotranspiration, air temperature, etc.) as inputs to a rain-
24 fall runoff model. Water use in all the sectors of the human endeavor will be determined in order to establish the water availability
RRE
25 given different climate change scenarios. Three catchments have been selected for this exercise. This paper therefore, presents the
26 background information, objectives and significance of the study, literature review, methodology, data collection and processing.
27 2004 Published by Elsevier Ltd.
28
29 1. Introduction equinoxes and eccentricity. The earth is tilted on its 37
rotational axis at an angle of 23.4 relative to a perpen- 38
30 There are three categories of climate change and these dicular to the orbital plane to the earth. This angle of 39
O
31 are: long-term, short-term and fluctuations. In 1941 inclination has fluctuated between 22 and 24.5 with 40
32 Milankovitch proposed a theory that identified the main an average periodicity of 41 thousand years. As the an- 41
33 cause of the Pleistocene ice ages (long-term climate gle of tilt increases, the amount of solar energy received 42
UNC
34 changes) as periodic changes in the distribution of at high latitudes over the summer season increases. The 43
35 incoming solar radiation resulting from variations in axis of rotation of the earth wobbles because of the 44
36 the earthÕs orbital geometry that is the tilt, precision of gravitational pull of the sun and moon on the equatorial 45
bulge on the earth. This wobble affects the timing of the 46
solstices and equinoxes in relation to the extreme earth 47
*
Corresponding author. Tel.: +268 518 4011; fax: +268 518 5276. sun distances. This phenomenon is known as precision 48
E-mail address: (J.I. Matondo).
1474-7065/$ - see front matter 2004 Published by Elsevier Ltd.
doi:10.1016/j.pce.2004.09.033
, JPCE 925 No. of Pages 11, DTD = 5.0.1
ARTICLE IN PRESS
17 September 2004 Disk Used
2 J.I. Matondo et al. / Physics and Chemistry of the Earth xxx (2004) xxx–xxx
49 of the equinoxes and affects the solar intensity of the sea- The greenhouse gases effect is expected to cause glo- 103
104
50 sons. The earthÕs orbit has varied from being near circu- bal warming which in turn will cause changes in average 105
51 lar to markedly elliptical with a mean periodicity of precipitation for any region in the order of plus or minus 106
52 about 9508 thousand years. These changes modulate ef- 20% (WMO/ICSU/UNEP, 1989). Generally it is ex- 107
53 fects of precision of the equinoxes. With maximum pected that floods now considered rare would occur 108
54 eccentricity, differences in solar radiation receipt of more frequently in certain regions while drought related 109
55 about 30% may occur between perihelion and aphelion. and competing water issues will intensify in other re- 110
56 Climate changes occurring over time scales shorter gions (Miller, 1989; Shaakee, 1989; IPCC, 1990). IPCC 111
57 than those associated with the orbital forcing frequen- (1990) report contends that higher temperatures may re- 112
58 cies are defined as short-term. Climate fluctuations on sult in more winter precipitation occurring as rainfall in- 113
OF
59 time scales of less than 100 years are usually considered stead of snow, thereby increasing winter season runoff 114
60 as climatic variability. and decreasing snow melt flows. Warmer temperatures 115
61 It has been considered that the major potential mech- may also affect snowmelt rates in spring and thus in- 116
62 anism of climate change over the next few hundred years crease spring season runoff. It has been established that 117
63 will be anthropogenic green house gas warming up. A climate change will cause impacts through changes in 118
RO
64 number of gases that occur naturally in the atmosphere rainfall distribution patterns, changes in magnitude 119
65 in small quantities are known as ‘‘greenhouse gases’’. and intensity of individual events, through changes in 120
66 Water vapour, carbon dioxide, ozone, methane, and ni- evaporation arising from temperature and radiation 121
67 trous oxide trap solar energy in much the same way as changes and thus changes in vegetation response. 122
68 do the glass panes of a greenhouse or a closed automo- Globally, the greenhouse gases effect is expected to 123
69 bile. This natural greenhouse gases effect has kept the elevate average precipitation by 5–15% and evapotran- 124
DP
70 earthÕs atmosphere some 30C hotter, than it would oth- spiration by 10–20% (WMO/ICSU/UNEP, 1989). How- 125
71 erwise be, making it possible for humans to exist on ever, at the local scale such as Swaziland, it is not known 126
72 earth. by how much precipitation, potential evapotranspira- 127
73 Human activities, however, are now raising the con- tion, temperature and runoff are going to change due 128
74 centrations of these gases in the atmosphere and thus to the greenhouse gases effect. 129
75 increasing their ability to trap energy. Carbon dioxide Therefore, there is a need to evaluate the impact of 130
76 levels have risen from 280 ppm by volume since before climate change on hydrology and water resources at 131
CTE
77 the industrial Revolution to about 360 ppm by 1990. the regional and local level and this is because water af- 132
78 Fuller (1997) reports that, carbon dioxide emission will fects all sectors of the human endeavour. The assess- 133
79 increase by 12% between 1990 and 1995. Man-made car- ment of the impact of expected climate change on 134
80 bon dioxide which, is the most important contributor to water resources involves the use of GCM models cou- 135
81 the enhanced greenhouse gases effect, comes mainly pled with hydrologic models (Kunz, 1993). This ap- 136
82 from the use of coal, oil, and natural gas. It is also re- proach will be used in the assessment of the impact of 137
83 leased by the destruction of forests and other natural climate change on hydrology and water resources in 138
RRE
84 sinks and reservoirs that absorb carbon dioxide from Swaziland. 139
85 the air.
86 According to the IPCC (1990), if countries around
87 the world do not reduce emissions of greenhouse gases 2. Background information 140
88 by the end of the next century:
Swaziland experiences a subtropical type of climate. 141
89 • Temperatures are expected to increase between 1 and It is therefore, characterised by wet humid summers 142
90 3.5 C, depending on population and economic and with cool dry winters. Most of the rains (75%) fall 143
91 growth. in the summer months (October–March) and about 144
O
92 • Sea levels are expected to rise between 15 and 90 cm, 25% falls in the winter months (April–September). The 145
93 with the best estimate being 50 cm and threatening 92 rainfall regimes that bring rainfall to Swaziland are: 146
94 million people each year with floods by the year 2100. convectional and tropical storms during summer and 147
UNC
95 • Mortality and illness will have risen as the intensity frontal showers during winter. Due to the physiographic 148
96 and duration of heat waves increased and as the trop- of the country, the Highveld and Middleveld and Lu- 149
97 ical habitat of mosquitoes that carry malaria and bombo Plateau regions receive high rainfall (800– 150
98 fever crept northward. 1200 mm annually). Therefore, these regions do experi- 151
99 • Rainfall will have decreased in some tropical and sub- ence flash floods in catchments originating from mount- 152
100 tropical areas and increased in others, significantly aineous areas especially during the rainy season. The 153
101 reducing food crops in developing countries as a Lowveld region receives less rainfall (500–700 mm annu- 154
102 whole. ally) and also experiences high temperatures. Rainfall in 155
ARTICLE IN PRESS
17 September 2004 Disk Used
Physics and Chemistry of the Earth xxx (2004) xxx–xxx
www.elsevier.com/locate/pce
2 Evaluation of the impact of climate change on hydrology and
3 water resources in Swaziland: Part I
OF
a,*
4 Jonathan I. Matondo , Graciana Peter a, Kenneth M. Msibi b
a
5 Water Resources Branch, Department of Geography, Environmental Science and Planning, University of Swaziland, Private Bag 4
6 Kwaluseni, Swaziland
PRO
b
7 Water Resources Branch, Swaziland
9 Abstract
10 It has been identified that, long-term climatic changes (Pleistocene ice ages) have been caused by periodic changes in the distri-
11 bution of incoming solar radiation due to the variations in the earthÕs orbital geometry, that is the tilt, precision of equinoxes and
12 eccentricity which take place with periodicity ranging from 41 to 9508 thousand years. However, it has been considered that the
13 major potential mechanism of climate change over the next few hundred years will be anthropogenic green house gas warming
TED
14 up. A number of gases that occur naturally in the atmosphere in small quantities are known as ’’greenhouse gases. Water vapour,
15 carbon dioxide, ozone, methane, and nitrous oxide trap solar energy in much the same way as do the glass panes of a greenhouse or
16 a closed automobile. This natural greenhouse gases effect has kept the earthÕs atmosphere some 30 C hotter, than it would otherwise
17 be, making it possible for humans to exist on earth. Human activities, however, are now raising the concentrations of these gases in
18 the atmosphere and thus increasing their ability to trap energy. The enhanced greenhouse gas effect is expected to cause high tem-
19 perature increase globally (1–3.5 C) and this will lead to an increase in precipitation in some regions while other regions will expe-
20 rience reduced precipitation (±20%). The impact of expected climate change will affect almost all the sectors of the human endeavor.
21 However, the major purpose of this project is to evaluate the impact of climate change on hydrology and water resources and estab-
C
22 lish the appropriate adaptation strategies for Swaziland. The impact of climate change on hydrology and water resources will be
23 evaluated using General Circulation Model results (rainfall, potential evapotranspiration, air temperature, etc.) as inputs to a rain-
24 fall runoff model. Water use in all the sectors of the human endeavor will be determined in order to establish the water availability
RRE
25 given different climate change scenarios. Three catchments have been selected for this exercise. This paper therefore, presents the
26 background information, objectives and significance of the study, literature review, methodology, data collection and processing.
27 2004 Published by Elsevier Ltd.
28
29 1. Introduction equinoxes and eccentricity. The earth is tilted on its 37
rotational axis at an angle of 23.4 relative to a perpen- 38
30 There are three categories of climate change and these dicular to the orbital plane to the earth. This angle of 39
O
31 are: long-term, short-term and fluctuations. In 1941 inclination has fluctuated between 22 and 24.5 with 40
32 Milankovitch proposed a theory that identified the main an average periodicity of 41 thousand years. As the an- 41
33 cause of the Pleistocene ice ages (long-term climate gle of tilt increases, the amount of solar energy received 42
UNC
34 changes) as periodic changes in the distribution of at high latitudes over the summer season increases. The 43
35 incoming solar radiation resulting from variations in axis of rotation of the earth wobbles because of the 44
36 the earthÕs orbital geometry that is the tilt, precision of gravitational pull of the sun and moon on the equatorial 45
bulge on the earth. This wobble affects the timing of the 46
solstices and equinoxes in relation to the extreme earth 47
*
Corresponding author. Tel.: +268 518 4011; fax: +268 518 5276. sun distances. This phenomenon is known as precision 48
E-mail address: (J.I. Matondo).
1474-7065/$ - see front matter 2004 Published by Elsevier Ltd.
doi:10.1016/j.pce.2004.09.033
, JPCE 925 No. of Pages 11, DTD = 5.0.1
ARTICLE IN PRESS
17 September 2004 Disk Used
2 J.I. Matondo et al. / Physics and Chemistry of the Earth xxx (2004) xxx–xxx
49 of the equinoxes and affects the solar intensity of the sea- The greenhouse gases effect is expected to cause glo- 103
104
50 sons. The earthÕs orbit has varied from being near circu- bal warming which in turn will cause changes in average 105
51 lar to markedly elliptical with a mean periodicity of precipitation for any region in the order of plus or minus 106
52 about 9508 thousand years. These changes modulate ef- 20% (WMO/ICSU/UNEP, 1989). Generally it is ex- 107
53 fects of precision of the equinoxes. With maximum pected that floods now considered rare would occur 108
54 eccentricity, differences in solar radiation receipt of more frequently in certain regions while drought related 109
55 about 30% may occur between perihelion and aphelion. and competing water issues will intensify in other re- 110
56 Climate changes occurring over time scales shorter gions (Miller, 1989; Shaakee, 1989; IPCC, 1990). IPCC 111
57 than those associated with the orbital forcing frequen- (1990) report contends that higher temperatures may re- 112
58 cies are defined as short-term. Climate fluctuations on sult in more winter precipitation occurring as rainfall in- 113
OF
59 time scales of less than 100 years are usually considered stead of snow, thereby increasing winter season runoff 114
60 as climatic variability. and decreasing snow melt flows. Warmer temperatures 115
61 It has been considered that the major potential mech- may also affect snowmelt rates in spring and thus in- 116
62 anism of climate change over the next few hundred years crease spring season runoff. It has been established that 117
63 will be anthropogenic green house gas warming up. A climate change will cause impacts through changes in 118
RO
64 number of gases that occur naturally in the atmosphere rainfall distribution patterns, changes in magnitude 119
65 in small quantities are known as ‘‘greenhouse gases’’. and intensity of individual events, through changes in 120
66 Water vapour, carbon dioxide, ozone, methane, and ni- evaporation arising from temperature and radiation 121
67 trous oxide trap solar energy in much the same way as changes and thus changes in vegetation response. 122
68 do the glass panes of a greenhouse or a closed automo- Globally, the greenhouse gases effect is expected to 123
69 bile. This natural greenhouse gases effect has kept the elevate average precipitation by 5–15% and evapotran- 124
DP
70 earthÕs atmosphere some 30C hotter, than it would oth- spiration by 10–20% (WMO/ICSU/UNEP, 1989). How- 125
71 erwise be, making it possible for humans to exist on ever, at the local scale such as Swaziland, it is not known 126
72 earth. by how much precipitation, potential evapotranspira- 127
73 Human activities, however, are now raising the con- tion, temperature and runoff are going to change due 128
74 centrations of these gases in the atmosphere and thus to the greenhouse gases effect. 129
75 increasing their ability to trap energy. Carbon dioxide Therefore, there is a need to evaluate the impact of 130
76 levels have risen from 280 ppm by volume since before climate change on hydrology and water resources at 131
CTE
77 the industrial Revolution to about 360 ppm by 1990. the regional and local level and this is because water af- 132
78 Fuller (1997) reports that, carbon dioxide emission will fects all sectors of the human endeavour. The assess- 133
79 increase by 12% between 1990 and 1995. Man-made car- ment of the impact of expected climate change on 134
80 bon dioxide which, is the most important contributor to water resources involves the use of GCM models cou- 135
81 the enhanced greenhouse gases effect, comes mainly pled with hydrologic models (Kunz, 1993). This ap- 136
82 from the use of coal, oil, and natural gas. It is also re- proach will be used in the assessment of the impact of 137
83 leased by the destruction of forests and other natural climate change on hydrology and water resources in 138
RRE
84 sinks and reservoirs that absorb carbon dioxide from Swaziland. 139
85 the air.
86 According to the IPCC (1990), if countries around
87 the world do not reduce emissions of greenhouse gases 2. Background information 140
88 by the end of the next century:
Swaziland experiences a subtropical type of climate. 141
89 • Temperatures are expected to increase between 1 and It is therefore, characterised by wet humid summers 142
90 3.5 C, depending on population and economic and with cool dry winters. Most of the rains (75%) fall 143
91 growth. in the summer months (October–March) and about 144
O
92 • Sea levels are expected to rise between 15 and 90 cm, 25% falls in the winter months (April–September). The 145
93 with the best estimate being 50 cm and threatening 92 rainfall regimes that bring rainfall to Swaziland are: 146
94 million people each year with floods by the year 2100. convectional and tropical storms during summer and 147
UNC
95 • Mortality and illness will have risen as the intensity frontal showers during winter. Due to the physiographic 148
96 and duration of heat waves increased and as the trop- of the country, the Highveld and Middleveld and Lu- 149
97 ical habitat of mosquitoes that carry malaria and bombo Plateau regions receive high rainfall (800– 150
98 fever crept northward. 1200 mm annually). Therefore, these regions do experi- 151
99 • Rainfall will have decreased in some tropical and sub- ence flash floods in catchments originating from mount- 152
100 tropical areas and increased in others, significantly aineous areas especially during the rainy season. The 153
101 reducing food crops in developing countries as a Lowveld region receives less rainfall (500–700 mm annu- 154
102 whole. ally) and also experiences high temperatures. Rainfall in 155
