Catchment Water Deficits and How to Close Them
Content Table
- Catchment Water Deficits and How to Close Them
- The Kafue River Basin
- The Thames Catchment: A River Basin at the Tipping Point
Introduction
Some years ago I was invited to work for six weeks with researchers at the New Mexico State University whose main interest was in water resources management. Within a few days we drove out to see the mighty Colorado River. They stood by our vehicles as I walked towards the river, puzzled both by being pushed out in front and by my friends grinning faces. I arrived at the river bank – and stepped across. The mighty Colorado was less than a metre wide.
This – for me – shocking experience led me to focus for several years on what I now refer to as “catchment water deficits”, that is river catchments where the flows of water have been very substantially reduced, not by declines in precipitation, but by humankind’s impacts on the river system.
I define a catchment water surplus as a situation in which, throughout the course of a specific year, total precipitation in a catchment (that is, a river basin) is sufficient to simultaneously satisfy four conditions:
1. Abstraction from the aquifer is maintained at a sustainable rate.
2. Outstream water fully meets the economic demand for water from households, agriculture, mining, manufacturing, construction and the services sectors.
3. The basin population’s economic demand for food is fully met from domestic rainfed and irrigated farming or from domestic fisheries or from food imports financed by the basin’s commodity and service exports.
4. The river’s instream flows do not fall below defined minima.
When a catchment water surplus does not exist, the river basin is in deficit.
It seemed important to me to try to apply these general criteria to at least two real-life situations. The rivers selected were the Kafue in Zambia and the Thames in England. My work on the Kafue was made possible only through the generous assistance of Scott Wilson Piesold, a British engineering firm. My work on the Thames was made possible through the generous assistance of W.S.Atkins, the Environment Agency, the Department for Environment, the Greater London Authority, ICID, and RWE Thames Water plc, as well as individuals cited in my publication The Price of Water: Studies in Water Resource Economics and Management, IWA, London 2007.
The Kafue River Basin
The Kafue River Basin is located entirely in Zambia in Africa (see Figure 1). It has an area of 157,000 km2 and its length is 1,300 km. At its junction with the Zambezi its discharge is approximately 300 m3/second. The Basin is conventionally divided into four regions: the Upper Kafue, the Middle Kafue, Kafue Flats, and the Lower Kafue. The Basin has a tropical climate with two distinct seasons: a wet season between November and March and a dry season between April and October. At the end of the wet season humidity is 75% and at the end of the dry season it is 45%. Mean daily temperatures vary from 13o and 20o Centigrade in July and between 21o and 30o in November. Sunshine hours during the dry season are 13 hours per day and are 7 hours per day in the wet season. The long-term average precipitation is 1,057 mm. Pan evaporation varies between 1900 mm and 2200 mm during the year. Effective precipitation is 53 mm (Scott Wilson Piésold 2003, Table 3.7).
In respect of groundwater, the best aquifers are associated with i) limestone formations around Lusaka and at locations in the Upper Kafue, including Mpongwe, and ii) the alluvial sands and gravels of the Kafue Flats, Lukanga Swamps, and the Nanzhila, Lufupa and Luswishi rivers. Groundwater potential is reported as a depth per unit area as follows: Upper Kafue 85mm/y, Middle Kafue 75mm/y, Kafue Flats 70mm/y, Lower Kafue 55mm/y. Groundwater is deemed private. Water abstraction is predominantly of surface water, although there is some groundwater abstraction for irrigation and rural domestic water supplies. Pumping water from mines for dewatering purposes takes place on a large scale, in order to facilitate copper production. One of the Kafue Basin’s copper mines is said to be the wettest mine in the world.
In respect of surface water, the immense discharge at the Zambezi of 300 m3/second is very much less than total rainfall. This is because of evaporation and transpiration from areas of impeded drainage and groundwater seepage zones, and because of high solar radiation in Zambia. Amongst the flood plains, swamps and marshy areas, Kafue Flats and Lukanga Swamps are the most significant. The Kafue Flats extend from Itezhi-Tezhi dam to the head of the Kafue Gorge, a distance of 260 km with a drop of only 6 metres. The Kafue Flats have an area of 6,500 km2 and the Lukanga Swamps’ area is 2,600 km2 at peak water level. There are also numerous dambos (local shallow depressions).
Hydroelectric power is an important regional (and national) resource. Itezhi-Tezhi reservoir and dam provides regulatory storage to enhance dry season flows and ensure firm energy availability for the downstream Kafue Gorge Upper (KGU) hydroelectric power station. In 2002 there was no power generation at Itezhi-Tezhi, which provides a live storage capacity of 6 thousand million cubic metres with a surface area of 390 km2. Downstream, the KGU reservoir, when fully impounded, has a surface area of some 800 km2 at 976.6 metres, and 257 km2 at 975.4 metres! The raised water level extends as far west as Nyimba, 115 km upstream. The power station is of 750 MW capacity and has gross and net storage of 900 million and 770 million cubic metres respectively. KGU’s energy output is estimated to be 3673 GWh/yr.
With respect to demography, in 1990 the Basin’s population was 2.9 million persons, 40 per cent of the Zambian total. The catchment is the most urbanised in Zambia. By the year 2000, Zambia’s population was estimated at 10.4 million; if the catchment’s proportion remained at 40 per cent, this would have given a basin population of 4.2 million in that year. Using the basin population for 1990 and 2000 above, there is a high estimated annual rate of growth of 3.8 percent. The rate of growth has been strongly impacted by immigration into a region offering many employment opportunities. However, the relative importance of natural growth and in-migration is not known.
Groundwater abstraction.
It is now appropriate to begin to test the hypothesis that the Kafue River Basin was in deficit in the year 2002. Considered in turn are groundwater abstraction, the economic demand for water, the population’s food requirements, and environmental needs.
Unfortunately there is no comprehensive account of groundwater abstraction for the Kafue River Basin. In 2002, data relating to pumping tests and borehole logging was not being collected. Scott Wilson Piésold comment: ‘Extensive aquifers are found within the basin particularly in the areas of the Copperbelt and Lusaka. Limited exploitation of these aquifers has taken place. Groundwater has been used on a local scale for urban water supply (Mazabuka and in the Copperbelt) and for rural water supply but surface water sources have formed the predominant source of supply’ (Scott Wilson Piésold 2003: 3.18). In rural areas the average yield of deep wells was limited by the capacity of hand pumps to six m3/day, which appears to be considerably below the minimum specific yield of most aquifers in the basin. The Scott Wilson Piésold study assumed the yield of shallow wells to be 2 m3/day. For the Basin as a whole, groundwater potential was estimated at 368 m3/second. This compares with a total demand for surface water and groundwater in 1995 of 32 m3/second.
We can now return to testing the theory of catchment water deficits set out in section one above. Condition 1 for the truth of the deficit theory is that abstraction from the catchment’s aquifers was not maintained at a sustainable rate. In fact the evidence shows that groundwater abstraction was sustainable. So condition 1 does not confirm the general hypothesis that the Kafue catchment was in water deficit in 2002.
The economic demand for water.
The economic demand for water by households, agriculture, mining, manufacturing, construction and the services sector is now considered. The economic demand for water refers to the volume of water that users are willing and able to purchase at the suppliers’ prices or charges. Table 1 shows the relative distribution between sectors of surface water abstraction rights. Agriculture is the dominant rights holder.
With respect to the industrial sectors, they either purchase water from the municipal water utilities or access their required supply by surface water abstraction. The utilities in 2002 made charges for water but use was not metered. Industry in general did not lack access to water, nor were water charges unaffordable.
With respect to the agricultural sector, access to water was secured by farmers pumping their own surface water and groundwater requirements. These own-supply costs were affordable.
With respect to the domestic sector, it is clear that in the Kafue River Basin in 2002 there was extensive poverty in the household sector (see section five below). However, there is no evidence that the purchasers of water were not able to secure what they were willing and able to purchase. What is striking about many of the African countries is the variety of forms of supply to users, particularly in urban areas, as well as the high proportion of income that the poor allocate to water purchases (Whittington et al. 1991, Merrett 2005: 106-131).
It is not suggested here that in some defined sense the people of the Kafue in 2002 had their needs for water met in full, in terms of quality or quantity. However, the second condition for deficit relates to economic demand, not need (Merrett 2005: 88-92). Survey work in Lusaka, in the Copperbelt towns and amongst rural households would certainly find widespread shortfalls of purchases in relation to the need for quality and quantity in water. But such shortfalls are manifestations of low income, they are not driven by insufficient quantities of surface water and groundwater flows.
Condition 2 for the truth of the deficit theory is that outstream water did not fully meet the economic demand for water from households, agriculture, mining, manufacturing, construction and the services sectors. In fact the evidence shows that the economic demand for water was fully met. So condition 2 does not confirm the general hypothesis that the Kafue catchment was in water deficit in 2002.
The supply of food.
In 1995, agriculture made up 17 per cent of the Kafue River Basin area, primarily on the eastern side of the basin. In the same year there were 85,000 farming households, mostly small and engaged in rainfed crops, crops and poultry, or crops, poultry and livestock. The large-scale operators are typically involved in double cropping, with rainfed cropping in the wet season (often with supplementary irrigation) and full irrigation in the dry season.
There were only 7 large or medium-scale irrigation projects in the basin in 1995. The total irrigated area was only 21,000 hectares, about 1 hectare in a thousand for the basin as a whole. There are important sectors for maize and the irrigation of sugar-cane (both for domestic consumption and for export). Major irrigation takes place at Mpongwe in the Upper Kafue. There is extensive fishing and livestock grazing (non-irrigated) and this is an important food source. Coffee is also produced. By 2002, there was evidence of an expansion and intensification of agriculture.
In 2002 the use of irrigation water was about one litre per second per hectare. This is an annual total volume of some 660 million cubic metres (mcm). The annual river flow at the Zambezi is about 9,450 mcm. So irrigation use is equal to about seven per cent of that downstream flow. The main irrigated crops are banana, coffee, cotton, rice, soybean, sugarcane, tea and wheat.
There is no evidence that the economic demand for food is not met, either by production within the Basin or by imports. Moreover, the Kafue River Basin exports copper and electricity on such a scale, in addition to its agricultural exports, that the Basin generates more than sufficient export income to finance its residual food needs from imported food at market prices.
However, there is widespread hunger and poverty throughout the catchment. Food insecurity is widespread in the Kafue Basin, particularly among farm households. We can certainly say that sufficient food is not produced for the population’s needs. But this is due neither to lack of water nor lack of land. Low farm productivity amongst small farmers and extensive urban poverty are the major issues. The argument here parallels that of section 4. The insufficiencies of food are not sourced by a lack of precipitation and instream water flows, they are rooted in low incomes.
Condition 3 for the truth of the deficit theory is that the basin population’s economic demand for food is not fully met from the domestic rainfed and irrigation sectors, domestic fisheries and food imports financed by the basin’s exports. In fact the evidence shows that the economic demand for food was fully met. So condition 3 does not confirm the general hypothesis that the Kafue catchment was in water deficit in 2002.
Environmental needs.
In 2002 no environmental requirements for the Kafue River Basin had been set by the Zambian water resource institutions. In that sense the river’s instream flows did not fall below defined minima and condition four for a catchment water deficit does not confirm the general hypothesis. In any case, Table 2 shows just how small were surface water abstraction rights in 2002-03 compared with the river’s flow and the basin’s groundwater potential.
Were environmental requirements to be introduced, they would almost certainly be defined in terms of water levels of the basin’s magnificent floodplains, swamps and marshes. The Kafue Flats and the Lukanga Swamps are the most significant of these vast ecosystems.
However, whereas there is no deficit-driven breach of environmental law, it is appropriate to refer to a different impact of the river’s development. Attention has already been drawn to the Kafue Gorge Upper and the considerable hydroelectric power generated there. To secure maximum power output, a secure flow of water into the Kafue Gorge is required. For this reason the hydroelectric sector has a powerful, long-term interest in maintaining the flow of the Kafue River. A catchment water deficit would be a disaster for the country’s electricity generation and its export of electric power.
This secure flow to the KGU is dependent, as has been shown in section 2 above, both on the reservoirs at the Gorge itself and those upstream at Itezhi-Tezhi. Unfortunately the Itezhi-Tezhi dam has reduced the depth, areal extent, duration and frequency of flooding in the whole of Kafue Flats. Moreover, recommendations to preserve the ecological balance of the Kafue Flats by release of a freshet from Itezhi-Tezhi dam of 300 m3/sec throughout the month of March each year have never been implemented. In part this is due to a smaller firm yield from the reservoir than in design documents - Itezhi-Tezhi dam is too low. Note that in this specific instance, the failure to meet an environmental recommendation is not because of deficit in the river’s flow but because of the manipulation of that flow for the requirements of hydroelectric power generation.
Condition 4 for the truth of the deficit theory is that the river’s instream flows do not fall below defined minima. Such minima do not exist. If they were to be introduced they would probably apply to the flooding parameters of the Kafue River Basin’s floodplains, swamps and marshes. In any case, condition 4 does not confirm the general hypothesis that the Kafue catchment was in water deficit in 2002.
Conclusions
This paper begins by setting out two hypotheses applicable to any of the world’s catchments and then tests the first, general, hypothesis on the Kafue River Basin. The general hypothesis in this case is that in 2002 the Kafue catchment was in water deficit. The hypothesis is verified if, in 2002, any one or more of the following propositions was true:
1. Abstraction from the catchment’s aquifers was not maintained at a sustainable rate.
2. Outstream water did not fully meet the economic demand for water from households, agriculture, mining, manufacturing, construction and the services sectors.
3. The basin population’s economic demand for food was not fully met from the domestic rainfed and irrigation sectors, domestic fisheries and food imports financed by the basin’s exports.
4. The river’s instream flows fell below defined minima.
In fact, it was shown that none of these four propositions was true. Therefore, in 2002 the Kafue River Basin was in surplus.
The application of the general theory to the specific circumstances of the Kafue River Basin has been instructive because it has shown both that the theory is testable (to destruction in this case!) and also that that some of the characteristics of a catchment water deficit exist even when no deficit exists. The author has particularly in mind the unmet need for water amongst poor households, widespread hunger, and changes in the flooding characteristics of the Kafue Flats. However, none of these realities can be ascribed to the catchment’s precipitation being insufficient to meet the river’s environmental needs, for groundwater to be pumped at a sustainable rate, for the economic demand for water to be satisfied and for the population’s food requirements to be met.
The case-study has also suggested ways in which to strengthen the causal hypothesis that defines the drivers of a catchment water deficit. It has become clear that in considering the water surplus or water deficit of catchments the focus should be carried out through what can be called the analysis of densities. Four such density measures are offered here as causal factors, drivers of surplus and deficit.
The first density measure we should deploy is the catchment’s population density in terms of persons per square kilometre. The more people and households in the resident population, the greater will be household use and consumption (evapotranspiration) of water. High density here pushes the catchment towards deficit.
The second density measure is the catchment’s production per square kilometre. The greater the level of production, the more water is used and consumed in the production of goods and services. High density here again pushes the catchment towards deficit.
The third density measure addresses irrigation head-on. Irrigation’s importance is that it uses about 70 per cent and consumes about 93 per cent of the world’s outstream supplies. Its density can be measured in various ways of which the best, perhaps, is irrigation water supplied to farmers, expressed as millimetres across the entire basin. Once again a high density pushes the catchment towards deficit.
The fourth density measure is precipitation in the basin expressed in millimetres. Total precipitation is proposed here, although a technically better variable would be what is called net precipitation in the original paper on catchment water deficits (Merrett 2005a: 143). Here, high density pushes the catchment towards surplus.
The fifth factor that is a driver towards surplus, not strictly a measure of density, is water productivity measured by net output in each economic sector divided by water consumed in the production process.
The Thames Catchment: A River Basin at the Tipping Point
In a paper published in 2005 an account is given of what is termed a ‘catchment water deficit’ (Merrett 2005a, Merrett 2005b). The concept is advanced in order to provide a methodological framework for research into catchments and river basins (the terms are used here interchangeably) in which the volume of river and groundwater flows are insufficient for the basin population’s requirements. A catchment water deficit is a situation in which, during the course of a specified year, total precipitation in a basin is insufficient to satisfy simultaneously the following four criteria:
1. Groundwater abstraction is maintained at a sustainable rate.
2. Outstream water fully meets the economic demand for water from households, agriculture, mining, manufacturing, construction and the services sectors. There is no assumption here that the set of charges and prices for water are fixed. Indeed, it may well be that in future river basin authorities will vary their charges and prices over time to deal, for example, with droughts. The capacity to adapt should be a central goal of river basin management.
3. The basin population’s economic demand for food is fully met from the domestic rainfed, irrigation and fishing sectors and/or from food imports financed by the basin’s commodity and service exports. The balance between food imports and food grown (and then consumed) in the basin is sure to vary from year to year. Again, the capacity to adapt is vital in water resource management.
4. The river’s instream flows do not fall below defined minima.
Criteria 1 and 4 are hydrogeological, hydrological and environmental. Criteria 2 and 3 are social, economic, commercial and agricultural. This comprehensiveness in the specification of deficits is unusual and may be considered to give the approach strength and relevance in the 21st century.
These four criteria are, perhaps, deceptively simple. With criteria 1 and 4, who is it that defines the sustainable flows? It may be that these are set by only a single institution, such as a catchment environment agency. However, when two or more organizations define the sustainable flows, the researcher may have to admit that accepting organization 1’s definition, the catchment is in surplus, whereas it is in deficit if one accepts organization 2’s definition. This author believes that, in fact, there is no acceptable, generic definition applicable to every river basin on the globe.The original paper referred to above suggested that global population growth and increases in output per head would drive ever more catchments throughout the world from surplus to deficit. By way of illustration, already in 2005 the Yellow River in Asia, the Nile in Africa, the Guadalquivir in Europe and the Río Bravo/Rio Grande in the Americas are all catchments in water deficit.
The Analysis of Densities
The significant advance achieved through the Kafue study was to strengthen understanding of the drivers to deficit and to surplus. These were weakly specified in the original paper. The author now believes that these drivers – causal variables – are best understood as a set of five densities, calculable for any and every river basin in the world once the necessary fieldwork is carried out. The densities are set out in Table 1.
Density 1, population density is equal to persons resident in the catchment divided by its area in square kilometres. It is a driver for deficit and creates this potential for deficit in two quite distinct ways. First, a bigger population is associated with a larger volume of domestic water used and thereby (partially) lost to evapotranspiration. Secondly, bigger populations require more food. These food needs may lead to greater requirements for irrigation output in the basin (see Density 3). Simultaneously, high population density may lead to a breach of criterion 3 for surplus as described in section one above. The catchment population may suffer from food shortages or need to turn to the international trade in agricultural produce in search of subsidized food.
Density 2, production density, is the value of output in the basin divided by its area. It is also a driver for deficit. Greater output is accompanied by greater supply and use of water in production, with consequential losses in evapotranspiration. Output here should exclude that from the irrigation sector as this sector appears as density 3.
Density 3, irrigation density, is the value of irrigation output in the basin divided by the catchment’s area. This is a special case of density 2 and made separate because of the intense evapotranspiration of irrigated agriculture. If we exclude evapotranspiration from reservoirs, Shiklomanov’s data suggest that at the global scale 93 per cent of hydrosocial evapotranspiration can be ascribed to irrigation and only 7 per cent to the urban sector’s domestic and production uses (Shiklomanov 2000: Table 5).
Density 4, effective precipitation, is a driver for surplus. The greater its value, the more likely is it that the river basin will be in surplus. Effective precipitation is equal to total precipitation less the catchment’s evapotranspiration, other than the evapotranspiration that occurs in household use and the production of output (see Table 1, footnote c).
Density 5, water productivity, is also a driver for surplus. It is defined as the catchment’s output value of goods and services divided by the evapotranspiration that takes place in producing that value. The catchment water deficit approach has a central concern with environmental flows; therefore it is primarily oriented neither to the supply of water nor to water’s use, but focuses on the losses to the river basin’s flows of water as a result of evapotranspiration. The appropriate measure of these losses in production should be the evapotranspiration that takes place between the point at which water is first abstracted from river and aquifer through to the recycling point of waste water and irrigation returns back to aquifer and river. Frederiksen’s and Perry’s critiques of water crisis solutions and irrigation efficiency studies have contributed powerfully to this orientation to evapotranspiration rather than water supply and use (Frederiksen 1996, Perry 1996). Catchment water deficits are powered by evapotranspiration.
The Thames River Basin
The original paper on catchment water deficits placed great emphasis on output growth per person and population increase driving river basins from surplus to deficit (Merrett 2005a: Table 8.2). Following completion of the work on the Kafue (see section 2 above), it made sense therefore to test deficit theory in a catchment known for its high densities of population and production. The Thames River Basin meets these criteria, yet exhibits no obvious symptoms of deficit. Karl Popper took the view that it is the falsification of theory that best drives scientific advance, so work on the Thames seemed to offer real benefits in testing the general theory (Popper 1959, Dow 2002: 85-90).
Hydrology of the Thames
The Thames River Basin is located in southern England (see Figure 1). The source lies in Gloucestershire, below the Cotswold Hills close to Cirencester, and the riverhead is 107 metres above sea level. The river finally flows to the North Sea to the east of London. The Thames’s length is 333 km from Thames Head Bridge to Shoeburyness in Essex. The Tidal Thames stretches from Teddington in the west of London to the North Sea. The mouth of the river is therefore at sea level. The river has many tributaries including the Windrush, the Kennet, the Cherwell, the Thame, the Wey, the Colne, the Mole and the Lee. There are 5,330 km of main river in the Basin and the catchment’s area is 13,000 km2 (www.environment-agency.gov.uk/regions/ thames/).
Long-term, annual total precipitation in the Basin is 690 mm. Long-term, annual effective precipitation is 280 mm. The latter figure is based on the 1961-90 average for the Berkshire Downs, derived from the Environment Agency’s use of CatchMod, their model of catchment hydrology. So the best estimate for long-term evapotranspiration is 410 mm. With respect to groundwater, the basin has extensive, water-rich, chalk and limestone aquifers. Surface water and groundwater cannot be abstracted without a permit from the Environment Agency. The right to abstract surface water is also conditional on the existence of minimal surface water flows at specified locations on the river and its tributaries.
Environment.
The Basin is the location of a wide range of environmental services and these generate substantial income for the public institutions and private companies that provide them. In particular the Environment Agency’s Thames Region welcomes each year millions of visitors. These include anglers, boating enthusiasts, canoeists, sailors, holiday-makers in hired craft, bird watchers and other naturalists, oarsmen and oarswomen, swimmers, sub-aqua divers, walkers and cyclists. The non-tidal Thames passes through 44 picturesque locks. There is a Thames Path National Trail. It meanders for 340 km from the river’s source, through both peaceful countryside as well as the Thames Valley’s villages and towns, and then on to the City of London, before ending at the Thames Barrier at Greenwich. There are also 462 Sites of Special Scientific Interest within the Thames River Basin.
Population and hydrosocial balance.
The catchment population in 2004 was 12.5 million. The Basin’s principal towns are Swindon, Oxford, Reading, Maidenhead and Greater London. The population of Greater London alone is 8.1 million persons. No recent estimate has been made of the river basin’s hydrosocial balance but one exists for the year 1994 and appears here as Table 2 (Merrett 1997: 17). (The hydrosocial balance for a specific year and area tabulates the volume of outstream water supplied from different sources and the volume of outstream water used by different user-groups.) In 1994 the main characteristics of the catchment in respect of the supply and use of outstream water were:
- Total volume of abstraction was about 1,880 million cubic metres.
- Water imports from and exports to other river basins were each about three per cent of total net supply.
- Surface water abstraction was the main source of supply.
- There was substantial leakage on the supply side.
- The domestic sector was by far the biggest user of water.
There are a number of users of water that access their supply themselves, by abstracting from the river flow and from local aquifers. All abstractions above a minimal limit are charged for by the Agency and these charges form a part of its annual income. The major abstractors are the water utilities, which face similar controls and charges as do non-utility abstractors.
In 2005 the Basin’s first desalination plant has been proposed for the London Borough of Newham on the Thames Estuary. At the time of writing London’s Mayor has vetoed the project on environmental grounds. If completed it would have a capacity of 150,000 m3/day, that is, 55 million cubic metres per year.
Production
No estimates have existed heretofore for the Basin’s economic output. However, the principal location of economic production in the Basin is the area of Greater London and data for the Greater London Authority does exist. The Office for National Statistics (2004) reports that London’s gross value added (GVA) for 2003 was £155 billion, with a GVA/head/year of £21,000. GVA is identical with Gross Domestic Product at basic prices. The percentage breakdown of the total by industry group is given in Table 3, which shows that services of various types dominate with 87 per cent of the total, whereas manufacturing, construction, mining and agriculture combined make up only 13 per cent of the total.
Estimates of regional GVA are on a residence basis, where the income of commuters is allocated to where they live rather than their place of work. Since commuting into London exceeds commuting out of London, the GVA statistics probably understate Greater London’s production. If we apply the £21,000 per capita data to the entire 12.5 million population of the Thames River Basin we have total output of about £260 billion per year at 2002 prices.
Water pricing
All outstream water supplied to the Thames River Basin’s customers is charged for. The utilities supplying the catchment are Thames Water, Three Valleys Water, South East Water, Sutton and East Surrey Water, and Essex and Suffolk Water. The charges set by Thames Water and these other private utilities are controlled by the Office of Water Services. For both households and business, provided that their supply is metered, there is both a fixed charge and a volumetric charge. In the domestic sector, if the supply is not metered then, in addition to the fixed charge, there is a charge for the supply of water based on the value of the property. In addition, there are wastewater charges. Thames Water suggests that the hot weather associated with climate change is increasing the economic demand for water and its use. Domestic use has risen from 150 litres per head per day (lhd) in the 1980s to 163 lhd in 2005. Single occupancy households are increasing and this also raises use per person. (www.thames-water.com/).
In most cases in the domestic sector, water is charged for on the basis of the value of the family’s house. Therefore the household water bill does not vary with use; there is no price of water. So, in these cases, no price-based, demand-side management of the use of domestic water exists.
The Thames in Water Deficit?
It is now appropriate to assess whether the Thames catchment is in surplus or in deficit. To begin with, this can be done by turning the four criteria of section one into four questions.
First, is groundwater abstraction maintained at a sustainable rate? The Environment Agency, as we have seen, has considerable regulatory powers to set limits on groundwater abstraction so that the rate of withdrawal does not exceed the sustainable yield within the basin. However, some parts of the aquifer have reached their sustainability limit; and ‘there are some abstractions which are thought to be unsustainable and these are being investigated (Environment Agency, pers.comm., 17th August 2005).
There is a more complex issue here. Hydrogeologists agree that the estimation of an aquifer’s sustainable yield rarely produces a single, unambiguous statistic. As Roger Calow of the British Geological Survey says, there are widely-placed error bars on most sustainable yield estimates (pers.comm. 22.10.05). In the case of the Thames, different sustainable yield constraints and, correspondingly, different rates of groundwater abstraction, lead to different environmental habitats. Which of these mutually-exclusive choices should be the base-line is therefore a matter of debate, particularly in relation to recorded historical changes in habitat over long periods of time. To sum up, there are cases of unsustainable groundwater abstraction in the Thames River Basin and there are cases where the sustainable yield is thought by environmentalists to be too high in historical retrospect.
Secondly, does outstream water fully meet the economic demand for water from households, agriculture, mining, manufacturing, construction and the services sectors? The answer is uncertain. It is more than ten years since restrictions were imposed on use, by limitations on spray irrigation or by limiting the use of hosepipes and garden sprinklers. However, the author is informed by the Environment Agency’s Head of Water Resources that “You will be aware, I hope, from the Environment Agency’s published reports, that Thames Water currently has a deficit of some 200 Ml/d; we are very concerned about security of supply” (pers.comm. 12.9.05). 200 Ml/d (megalitres per day) is equal to 73 million cubic metres per year.
Thirdly, is the basin population’s economic demand for food fully met from the domestic rainfed, irrigation and fishing sectors and/or from food imports financed by the basin’s commodity and service exports? Food output in the catchment is small in comparison with food purchases by the basin’s population of 12.5 million. However, the region’s exports of services are vast, both to the rest of the U.K. and to the world. In fact, London and New York may well be the world’s two largest urban producers of services for export. Finance, banking, tourism, the arts, research and education flourish as exporting sectors. The basin’s exports are more than sufficient to meet its net food requirements. Therefore the population of the Thames River Basin has no difficulty whatsoever in accessing at the market price all the food it wants and can afford to purchase.
Fourthly, do the river’s instream flows meet defined minima? The author has not received any evidence from the Environment Agency that river flows regularly fall below these minima as a result of excessive surface water abstraction. However, in October 2004 an Environment Agency officer suggested that the abstraction levels in the Thames River Basin were ten per cent higher than ideal from an environmental perspective (London Assembly Environment Committee 2004: 5).
But it is also necessary to consider the export and import of water in the Basin. In 2004 imports were negligible whereas exports, primarily to the Anglian Region, were about 40 million cubic metres. (Environment Agency, pers.comm. 17.10.2005).
To sum up, in 2005 the Thames River Basin is a catchment in water deficit, but only at the margin.
The Density Analysis of the Thames River Basin
The Thames catchment is modest in size, has a large population, and has vast total output. Despite this, the basin in 2004 and 2005 appears to be only modestly in deficit. In comparative terms, the river is certainly in a far, far healthier state than, for example, the Murray-Darling, the Yellow River, the Nile, the Guadalquivir and the Río Bravo/Rio Grande. This conundrum should be possible to explain using density analysis. Table 4 provides the estimates for the Thames of the five density drivers set out and defined in Table 1.
Population density is about 960 persons per square kilometre. In comparison with the rest of the world’s river basins this is extremely high. Figure 1 shows how large is Greater London in comparison with the scale of the river basin. Table 5 shows that, amongst countries with a population of five millions or more, England is the fifth most-densely populated in the world. The population density of the Thames River Basin is 3.4 times greater than that of the rest of England. Put another way, if the Thames River Basin were a country it would be the second most densely populated in the world.
Production density is £20 million per square kilometre, extraordinarily high. When we have a broad range of global data of this type, it may prove that the Thames has the highest production density of any catchment in the world.
The first two drivers to deficit are powerful but the third, irrigation density, is extremely weak. The scale of irrigation in the catchment is small. Unfortunately there is no published output value, but we do have data on the scale of irrigation water use. The Environment Agency Thames Region (EATR) states that in 2003 the licensed volume for agricultural spray irrigation was 11,321,000 m3 (EATR pers.comm. 21.7.05). (The licensed quantities for general agriculture, fisheries and watercress were 8,730,000 m3.) Even if all of this irrigation use is lost to evapotranspiration, the flow is still slightly less than 1 mm when expressed across the river basin.
Turning to the drivers for surplus, we see that effective precipitation is rather high in global comparative terms. The catchment has a humid climate with moderate average temperature and wind speeds.
Finally, an attempt is made to estimate water productivity at the catchment scale. This variable, in terms of the definition given in section three, has probably never been estimated before - anywhere. The data are fairly crude, particularly the volume of water used in production and the suggested 20 per cent evapotranspiration losses in use. But the value of this density driver is so large that even a substantial adjustment, following the necessary fieldwork, would still leave a value almost incredible in its size. So it is useful to restate what that value means:
The ratio of the gross value added in the production of goods and services in the Thames River Basin to the number of cubic metres lost to the catchment in the evapotranspiration of water used for production probably exceeds £1700/m3.
In 2004-2005, the volumetric charge for water supplied to non-domestic customers by RWE Thames Water was £0.65 per cubic metre, or £3.25 for each five cubic metres. Therefore the ratio of gross value added to the cost of water supplied was 523 to 1! This allows for the fact that every five cubic metres supplied represents only one cubic metre consumed. Put another way, non-domestic users cost of water was some 0.2 per cent of gross value-added.
There is another way of expressing water productivity at the basin scale, although it does not permit inter-basin comparisons. Across the Thames River Basin, for every millimetre of water lost to evapotranspiration during the course of output production, the value of that production is £20,000,000,000!
Tipping Deeper into Deficit
It is argued above that the Thames River Basin is in deficit but that the situation is not yet desperate, despite the region’s high population density and production density. This is because the catchment is fairly humid and because production recycles back to the river basin about 80 per cent of the water used in the production process, with a consequentially high value of water productivity.
The high rate of recycling exists in part because of the modest scale of irrigation. The minimal scale of plant production (either rainfed or irrigated) is possible because the basin population of 12.5 million exports sufficient goods and services – particularly the latter – so that it faces no financial or economic difficulty in importing food produced in other river basins. Those imports themselves require rainfall and/or irrigation for their growth, of course, but the evaporative losses take place in other catchments, not in the Thames River Basin.
However, the author believes that we are now in the early stages of a tipping process during which the severity of the catchment’s water deficit will accelerate. This shift in
severity is sourced by three dynamic forces: climate change, population growth and production growth. Climate change will bring with it hotter, drier summers and warmer wetter winters. Summer heat and low humidity will reduce effective precipitation, impacting severely on river flows and groundwater recharge (Collingwood 2005). Population growth in the South-East, a region that overlaps with the Thames River Basin, will drive up total household use. The South-East England Regional Assembly announced in 2005 plans to build 578,000 new homes in the region (Guthrie 2005). Pressure for growth at the eastern limit of the Thames River Basin will also arise from the siting of the 2012 Olympic Games on the River Lee, the Thames’s most easterly tributary. Production growth will drive and be driven by population growth. In particular this will occur in the site area of the Olympic Games as well as in Thurrock, Essex, where the biggest container port in Britain is to be constructed. Thurrock is on the Thames and, technically, a dozen miles east of the basin’s limit (Blitz 2005).
In the light of these dynamic forces within to the Basin, redemptive options need to be examined. There are just six such options, widely varying in their political feasibility and desirability (Merrett 2005a: 75-76):
1. The deceleration and reversal of the rate of growth of population.
2. The deceleration and reversal of the rate of growth of production.
3. Further increases in water’s productivity.
4. The introduction of universal metering, to reverse the volume of household use per person.
5. The reduction of evaporative losses both from reservoirs and from water supply leakage; groundwater re-charge has advantages here.
6. An enhanced capacity of the Environment Agency in its forward planning and its policy instruments, including the routine use of the hydrosocial balance in forecasting.
Certain palliative options also exist. One is to reduce the environmental standards relating to groundwater and surface water abstraction. These will, quite properly, be opposed by the environmental movement. A second is to increase water re-use; but this can only be beneficial if it reduces evapotranspiration losses and this may not occur. This is a policy area deserving new research. A third is rainwater harvesting, but this is just surface water or groundwater abstraction under another name. A fourth is importing water from other catchments. But this may drive other catchments into deficit and it is also costly in construction terms as well as demanding in terms of the electricity required for pumping. Electricity generation is not carbon-neutral. A fifth is the desalination of sea-water, as in the case of the proposed plant in the London Borough of Newham. Again this requires expense and substantial electricity inputs.
Conclusion
It is the opinion of the author that the two roads to redemption from the threat of much greater Thames River Basin deficits in the future are to severely limit the housebuilding programme in the catchment and to introduce the universal metering of household water use. As Jay O’Keeffe suggests, water resource management should be like the construction of a cathedral; one approaches it within the perspective of the very long run.
References
The Kafue:
Scott Wilson Piésold (2003), Integrated Kafue River Basin Environmental Impact Study Main Report, Ashford: Scott Wilson Piésold.
Whittington, D., Lauria, D. & Mu, X. (1991) ‘A study of water vending and willingness to pay for water in Onitsha, Nigeria’, World Development 19 (179-198).
The Thames:
Blitz, R. (2005). £1.5 bn boost for sea freight. Financial Times 21 July 2005.
Collingwood Environmental Planning and Land Use Consultants (2005). SEERA Climate Change Adaptation and Mitigation Implementation Plan: Consultation Draft. South-East England Regional Assembly, London.
Dow, S.C. (2002). Economic Methodology: an Inquiry. Oxford University Press. Oxford.
Frederiksen, H.D. (1996). Water crisis in developing world: misconceptions about solutions. Journal of Water Resources Planning and Management, 122 (2): 79-87.
Guthrie, J. (2005). Homes will not ruin countryside, says minister. Financial Times 17-18 September.
London Assembly Environment Committee (2005.) Down the Drain: London’s Water Usage and Supply. LAEC, London.
Merrett, S. (1997). Introduction to the Economics of Water Resources: an International Perspective. UCL Press, London.
Merrett, S (2005a). The Price of Water: Studies in Water Resource Economics and Management. International Water Association, London.
Merrett, S. (2005b). Catchment water deficits in the 21st century. Water Policy, 7 (2): 141-149.
Merrett, S. (2005c). Catchment water deficits: an application to Zambia’s Kafue River Basin. Water Policy (forthcoming)
Office for National Statistics (2004). Regional Gross Value Added. ONS, London.
Perry, C. (1996). The IIMI Water Balance Framework: a Model for Project Level Analysis. International Irrigation Management Institute, Colombo.
Popper, K. (1959). The Logic of Scientific Discovery. Hutchinson, London.
Scott Wilson Piésold (2003). Integrated Kafue River Basin Environmental Impact Study: Main Report. Scott Wilson Piésold, Ashford.
Shiklomanov, I.A. (2000). Appraisal and assessment of world water resources. Water International, 25 (1): 11-32.
www.environment-agency.gov.uk/regions/thames/
Figure 1 caption
Figure 1: Map of the Thames River Basin
Related Articles
