1 00:00:01,420 --> 00:00:05,220 Welcome to the submodule, Water for urban development. 2 00:00:05,300 --> 00:00:07,300 My name is Marie-claire ten Veldhuis. 3 00:00:07,940 --> 00:00:12,620 I work as an assistant professor for urban water systems, at Delft University of Technology. 4 00:00:14,080 --> 00:00:17,490 People need water to live and survive. 5 00:00:17,490 --> 00:00:22,200 In urban areas large numbers of people are living together in high concentrations and 6 00:00:22,200 --> 00:00:24,360 they need a lot of water. 7 00:00:24,360 --> 00:00:28,099 How do citizens get access to sufficient volumes of water? 8 00:00:28,099 --> 00:00:31,109 Where do cities get their water supply from? 9 00:00:31,109 --> 00:00:35,409 Are cities suffering from water stress or are waters suffering from urbanisation? 10 00:00:36,400 --> 00:00:40,380 In this submodule we will have a look at how cities and water systems interact. 11 00:00:41,420 --> 00:00:45,410 Since 2010, more than 50% of the world population is living 12 00:00:45,410 --> 00:00:49,230 in cities and this number is expected to rise in the next decades. 13 00:00:50,080 --> 00:00:54,900 Cities face the challenge of meeting water demands of their growing populations. 14 00:00:55,740 --> 00:00:58,680 So how much water does a city actually need? 15 00:00:59,480 --> 00:01:04,200 A good starting point to estimate urban water needs is to multiply the urban population 16 00:01:04,210 --> 00:01:07,020 by the average daily water use per person. 17 00:01:07,820 --> 00:01:11,600 This is also referred to as the per capita water use. 18 00:01:12,200 --> 00:01:17,820 Water use patterns vary a lot between countries, regions and even within cities, 19 00:01:17,830 --> 00:01:21,110 depending on access to drinking water, availability of water and costs. 20 00:01:21,830 --> 00:01:22,990 For instance, in Mumbai, 21 00:01:22,990 --> 00:01:26,860 India, per capita water use is 15 times higher in 22 00:01:26,870 --> 00:01:30,790 high-income suburbs with good water access compared to slum areas. 23 00:01:31,430 --> 00:01:34,940 Worldwide, average water use per person varies from less 24 00:01:34,940 --> 00:01:39,120 than 50 litres per day to over 500 litres per day. 25 00:01:39,780 --> 00:01:42,740 These numbers include direct consumption of water, 26 00:01:42,740 --> 00:01:46,950 bathing and showering, water usage for washing clothes and dishes 27 00:01:46,950 --> 00:01:48,330 and garden watering. 28 00:01:49,520 --> 00:01:54,800 Now let’s have a look at two different cities and estimate how much water is used by their citizens. 29 00:01:56,100 --> 00:01:59,500 Rotterdam is the second largest city in the Netherlands, 30 00:01:59,500 --> 00:02:02,409 located in the Rhine delta, at the North Sea coast. 31 00:02:02,409 --> 00:02:07,570 Jakarta is the capital of Indonesia, located in the delta of the Citarum and several 32 00:02:07,570 --> 00:02:09,190 other rivers. 33 00:02:09,190 --> 00:02:12,980 Rotterdam is a modern, industrial city with a large port area, 34 00:02:12,980 --> 00:02:18,860 Jakarta is a rapidly growing metropolis with large variations in economic development between 35 00:02:18,860 --> 00:02:20,340 the city’s neighbourhoods. 36 00:02:21,000 --> 00:02:25,720 Now let’s make an estimate of domestic water use for these two cities and answer the following 37 00:02:25,720 --> 00:02:30,680 questions: - How large is the urban population of Jakarta and Rotterdam? 38 00:02:31,780 --> 00:02:34,900 - What is the average domestic water use? 39 00:02:34,900 --> 00:02:38,629 - What is the total water need of the city’s population? 40 00:02:38,629 --> 00:02:42,260 - What is the main source of domestic water use for the urban population? 41 00:02:43,040 --> 00:02:45,760 First, we’ll fill in some numbers for general characteristics 42 00:02:45,760 --> 00:02:48,100 of the cities of Rotterdam and Jakarta. 43 00:02:48,640 --> 00:02:52,720 Total population, size of the city area, 44 00:02:52,730 --> 00:02:56,830 population density and average domestic water use. 45 00:02:57,580 --> 00:03:04,780 From these numbers we can compute average daily water use and total yearly water use. 46 00:03:05,580 --> 00:03:12,220 To get a grasp of these numbers: 1 million m3 water is about the equivalent in volume 47 00:03:12,220 --> 00:03:15,380 of 250 olympic swimming pools. 48 00:03:16,120 --> 00:03:21,200 These volumes of water need to be made available in the city or need to be transported there, 49 00:03:21,209 --> 00:03:22,449 if not available locally. 50 00:03:24,020 --> 00:03:28,300 Let’s look at some potential sources of water for Rotterdam and Jakarta and see how 51 00:03:28,310 --> 00:03:33,910 they compare to the daily and yearly domestic water use estimates we just found. 52 00:03:35,180 --> 00:03:39,560 A first option is using rainfall that directly falls on the city’s surface. 53 00:03:40,560 --> 00:03:42,720 Jakarta, located in the tropics, 54 00:03:42,730 --> 00:03:49,030 receives a lot of rainfall: on average, 1850 mm yearly. 55 00:03:49,030 --> 00:03:51,450 Rotterdam, with a moderate climate, 56 00:03:51,450 --> 00:03:55,310 gets less rainfall, about 850 mm. 57 00:03:55,310 --> 00:03:57,700 If we multiply this by the city’ surface area, 58 00:03:57,700 --> 00:04:01,920 we’ll find the total yearly available amount of rainwater. 59 00:04:03,400 --> 00:04:07,959 As we can see by comparing the numbers, there is more than enough rainwater to cover 60 00:04:07,959 --> 00:04:11,629 the city’s water needs, on an annual basis. 61 00:04:11,629 --> 00:04:14,949 That is, if we would be able to capture all rainwater. 62 00:04:15,960 --> 00:04:20,760 And if rainfall would be spread nicely and evenly over all days of the year. 63 00:04:22,210 --> 00:04:26,000 Another potential source of water, as we saw in a previous submodule, 64 00:04:26,000 --> 00:04:26,860 is groundwater. 65 00:04:28,040 --> 00:04:32,460 Available groundwater resources depend on natural replenishment by rainfall, 66 00:04:32,460 --> 00:04:36,849 size of the groundwater basin and thickness of the ground layers that groundwater can 67 00:04:36,849 --> 00:04:38,189 be pumped from. 68 00:04:38,980 --> 00:04:43,400 And it depends on the quality, too: groundwater near the sea turns saline 69 00:04:43,400 --> 00:04:48,360 as a result of salt intrusion and is not suitable for most water uses. 70 00:04:49,140 --> 00:04:53,220 This is why groundwater in the Rotterdam region is not used for consumption. 71 00:04:53,940 --> 00:05:00,699 In Jakarta estimates of groundwater availability and use vary as there are many private abstractions 72 00:05:00,699 --> 00:05:04,999 on top of the larger abstractions for industry and drinking water production. 73 00:05:05,860 --> 00:05:12,159 It is estimated that about 60 million m3 of groundwater is abstracted annually for Jakarta’s 74 00:05:12,159 --> 00:05:13,300 water supply. 75 00:05:13,860 --> 00:05:17,420 This is by no means sufficient to meet total water needs. 76 00:05:18,840 --> 00:05:22,499 River water is an obvious third source of water, 77 00:05:22,499 --> 00:05:25,539 especially in delta cities like Jakarta and Rotterdam. 78 00:05:26,280 --> 00:05:31,819 Rivers in both cities transport water from large upstream catchments. 79 00:05:31,819 --> 00:05:35,319 In Rotterdam, the Rhine and Meuse rivers transport approximately 80 00:05:35,319 --> 00:05:42,189 80 billion of m3 annually and in Jakarta about 6 billion m3 of water flow through Citarum 81 00:05:42,189 --> 00:05:43,900 rivers, on average. 82 00:05:45,249 --> 00:05:48,529 This is more than enough to cover urban water needs. 83 00:05:48,960 --> 00:05:52,120 But like rainfall, river flows are not equally distributed over 84 00:05:52,129 --> 00:05:55,169 the year, so intermediate storage is needed to cover 85 00:05:55,169 --> 00:05:56,429 periods of low flow. 86 00:05:58,320 --> 00:06:00,600 So what can we conclude from these numbers? 87 00:06:00,610 --> 00:06:05,050 First, that in Jakarta and Rotterdam annual rainfall 88 00:06:05,050 --> 00:06:08,090 in principle is sufficient to cover the cities’ water needs. 89 00:06:08,980 --> 00:06:14,060 Groundwater availability is limited and cannot on its own cover total water needs. 90 00:06:14,919 --> 00:06:18,569 River water is the largest source of water for the two delta cities, 91 00:06:18,569 --> 00:06:21,990 yet most of this water comes from large upstream catchments. 92 00:06:21,990 --> 00:06:24,789 Here, the city is competing with many other water 93 00:06:24,789 --> 00:06:27,729 demands, especially from agriculture. 94 00:06:29,180 --> 00:06:33,340 Domestic water use is small compared to water use by other sectors. 95 00:06:33,900 --> 00:06:38,839 Globally, domestic water use represents about 5-10%, 96 00:06:38,839 --> 00:06:44,169 industry about 15% and agriculture up to 80% of total water use. 97 00:06:44,580 --> 00:06:48,539 Again, these figures vary widely from region to region, 98 00:06:48,539 --> 00:06:53,289 depending on agricultural and industrial activity and water availability. 99 00:06:53,289 --> 00:06:57,809 In Northwestern Europe, for instance, agriculture represents less than 16% of total 100 00:06:57,809 --> 00:07:01,819 water use and more than half is used by industry. 101 00:07:01,819 --> 00:07:05,699 In most tropical regions, agriculture is the main water using sector 102 00:07:05,699 --> 00:07:09,719 by far, representing up to almost 100% of total water use. 103 00:07:11,360 --> 00:07:15,499 Back to our two cities, what water resources are they using to cover 104 00:07:15,499 --> 00:07:17,679 domestic water needs? 105 00:07:18,369 --> 00:07:22,179 In Jakarta and Rotterdam, river water is the main source used to cover 106 00:07:22,179 --> 00:07:24,409 urban water needs. 107 00:07:24,409 --> 00:07:28,509 Because river flows are fluctuating between wet and dry periods, 108 00:07:28,509 --> 00:07:30,800 large reservoirs have been constructed in both cases, 109 00:07:30,800 --> 00:07:33,840 to store water and overcome periods of low flow. 110 00:07:35,020 --> 00:07:38,619 In Jakarta, river water is supplemented with groundwater 111 00:07:38,619 --> 00:07:44,649 abstracted from a few large wells and a lot of individual small wells at household level. 112 00:07:45,560 --> 00:07:50,220 An important reason for construction of these wells is the insecurity of Jakarta’s central 113 00:07:50,229 --> 00:07:51,589 water supply. 114 00:07:52,280 --> 00:07:54,160 Interestingly, rainfall, 115 00:07:54,160 --> 00:07:59,040 a large source of locally available water in both cities is not used by the 116 00:07:59,050 --> 00:08:00,969 city’s households. 117 00:08:00,969 --> 00:08:02,740 This applies to most cities worldwide: most cities are using river water, 118 00:08:02,740 --> 00:08:07,159 very few cities are using rainwater as a water resource. 119 00:08:07,920 --> 00:08:12,599 Now the question REMAINS: Why are cities not using clean, 120 00:08:12,599 --> 00:08:15,099 locally available rainfall to cover their water needs 121 00:08:16,740 --> 00:08:20,860 Part of the explanation is to be found in historical development. 122 00:08:20,860 --> 00:08:25,119 The following images illustrate how cities, as they grow, 123 00:08:25,119 --> 00:08:28,959 take in water from an increasingly large part of their surroundings. 124 00:08:28,959 --> 00:08:33,099 They start using groundwater as this is a more or less constant, 125 00:08:33,099 --> 00:08:35,130 locally available source of water. 126 00:08:35,130 --> 00:08:38,750 Gradually, local groundwater resources get contaminated 127 00:08:38,750 --> 00:08:41,550 and may even get depleted. 128 00:08:41,550 --> 00:08:47,060 This means water needs to be taken elsewhere and transported to the city. 129 00:08:47,060 --> 00:08:51,680 Groundwater is abstracted from the surrounding region and when this is no longer sufficient, 130 00:08:51,680 --> 00:08:54,340 river water is used as a supplement. 131 00:08:54,340 --> 00:09:00,090 This means constructing large dams to create reservoirs and store water to overcome periods 132 00:09:00,090 --> 00:09:01,790 of low river flow. 133 00:09:01,790 --> 00:09:04,160 Somehow, in this process, 134 00:09:04,160 --> 00:09:09,120 rainwater is forgotten as a potential, locally available resource. 135 00:09:10,360 --> 00:09:15,670 In large cities worldwide, some 1.2 billion people primarily depend on 136 00:09:15,670 --> 00:09:17,120 river water sources. 137 00:09:17,780 --> 00:09:20,720 The remainder, about 20% of the urban population, 138 00:09:20,720 --> 00:09:22,490 depends mainly on groundwater. 139 00:09:22,490 --> 00:09:26,940 While groundwater is mostly drawn from within or close to the city boundaries, 140 00:09:26,940 --> 00:09:29,340 river water is taken from much larger catchment areas. 141 00:09:30,500 --> 00:09:34,520 Urban areas cover about 2 to 4% of the Earth’s land surface. 142 00:09:35,260 --> 00:09:40,760 Upstream areas used for their water sources, their urban water footprints, 143 00:09:40,770 --> 00:09:43,850 cover more than 40% of the Earth’s surface. 144 00:09:44,620 --> 00:09:47,860 So worldwide, the urban water footprint is about 10 times 145 00:09:47,860 --> 00:09:49,760 the size of the actual cities. 146 00:09:51,450 --> 00:09:55,550 Bringing large volumes of water to the cities from such extensive areas requires a lot of 147 00:09:55,550 --> 00:09:56,750 water infrastructure. 148 00:09:57,580 --> 00:10:03,460 It is estimated that globally cities transport more than 500 billion of water liters daily 149 00:10:03,470 --> 00:10:07,490 over a total distance of 27,000 kilometers. 150 00:10:08,010 --> 00:10:11,900 When laid in a straight line, urban water infrastructure could stretch halfway 151 00:10:11,900 --> 00:10:13,260 around the globe. 152 00:10:13,260 --> 00:10:17,320 Even so, many large cities are under water stress and 153 00:10:17,320 --> 00:10:20,450 cannot always supply their citizens and economic activities with sufficient water. 154 00:10:23,760 --> 00:10:25,260 As cities continue to grow, 155 00:10:26,070 --> 00:10:29,770 new solutions will have to be found to meet urban water needs. 156 00:10:29,770 --> 00:10:36,290 Rainwater harvesting and water reuse are examples of new developments that will help to quench 157 00:10:36,290 --> 00:10:40,010 cities’ thirst in a more sustainable way in the future.