Capítulo II. La técnica: fases de cada una de las pruebas atléticas de campo
2.5 El lanzamiento de peso
My thesis aimed to obtain a better understanding of the sectorial water use development in a densely-urbanized delta region. I developed a conceptualization of water use to assess the contribution of sectorial water needs in the reported water shortage events in the PRD, and to explore the possibility of using water use as an adaptive measure to alleviate the risk of severe salt intrusion. Furthermore, I developed a method to generate regional water scenarios consistent with global scenario assumptions. With these regional water scenarios, I could evaluate water balance dynamics in the future, to help safeguard the access to fresh water, while sustaining the fast population and socio-economic growth.
Observational data documented in various government reports and statistic yearbooks have been collected for my study and presented in this thesis, such as sectorial water use data and water use intensities. These data are subject to uncertainties and measurement errors. Reporting the comprehensive overview of sectorial water use data is new in China, and as a result date back to only the end of 1990s. I selected the generally well documented data from 2000, but not all the sectors are covered by the report, while the statistical categorization of sub-sectors such as urban and rural domestic were modified several times.
On the other hand, however, every time when the statistical categorization is changed, the new categories suit better the developments in society. For instance, the domestic water use is changed from domestic urban and rural residential water use before 2003, to urban public water use and residential water use till 2008. Since 2009, the domestic sector has been changed into three sub-sectors: urban public water use, urban residential water use, and rural residential water use. With these new categories, my model can simulate the urban and rural domestic water use separately according to the differentiated income, and simulate urban public water use that probably relates to the overall GDP of the city. More importantly, urban public water demands could be fulfilled by recycled grey water instead of blue
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water from the river. That is, such new statistics, make it possible to include water re-use into the model framework.
Nevertheless, due to data limitations, my study reflects only part of the dynamics of regional water use because of an incomplete set of water using sectors selected. For example, capturing dynamics of water use in electricity production sector is not feasible with the available data. However, electricity production is the second largest water user in China following agriculture (Feng et al. 2014). In the PRD, the electricity production requires about 13% of the total water use. Population and socio-economic growth in future will directly increase the water use, but will also increase energy demand and thus indirectly further increases water use (Feng et al. 2014, Gu et al. 2016). At least some basic information on power plants is required to refine the current framework to estimate the water use for thermoelectricity production, e.g. number and installed capacity, the type of cooling system used, as well as scenarios for future power generation techniques (thermoelectric vs renewables).
Data limitation also affects the accuracy of estimated sectorial water use dynamics. Manufacturing water use intensity, for instance, heavily depends on the structural composition of the industries included in the region, and the water saving technologies adopted. Disaggregating the sub-manufacturing sectors with sufficient data, the equation used in estimating manufacturing water use could possibly be adjusted for each individual sub-sector, thus greatly increasing the accuracy of the estimation, and could thus provide comprehensive information for optimizing structural changes in the region’s industrialization.
The conceptualization framework used in this thesis is largely based on equations from the WaterGAP model, a state-of-the-art global water resource model system with sophisticated modules for sectorial water use assessment. WaterGAP links sectorial water use with the underline socio-economic drivers. It is a valuable tool to capture the development trends of water use on regional level, as its input data are coarse enough to be available on regional scale, yet fine enough to capture the sectorial water use dynamics.
However, sub-sectorial scale processes and inter-(sub)sector influence is missing in the current model framework. With sufficient data support, the sectorial water use module could be upgraded with higher temporal and sub-sectorial resolution. The high-resolution estimation may provide new insights of how the sub-sectors could
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Modelling such inter-sectorial water re-use requires intensive well-reported data of water quantity, water quality, and production processes, etc. But it is possible to start from a few key water user sectors that are the main water users. For instance, using domestic effluent or processed industrial wastewater for irrigation.
The procedure proposed in this thesis for generating regionally specific water scenarios could downscale the assumptions and data produced in global assessment, yet well capture the future dynamics on regional level. A key requirement for downscaling is to incorporate sufficient regionalyl specified development records and future targets and planning. On one hand, what is lacking in this thesis, is the long-term planning for socio-economic growth in the PRD beyond 2020, which may compromise the ability of long-term projection to capture the regional specified development.
On the other hand, regionally specified development targets may take an inward perspective only , thus overlooking the requirements of neighbouring regions. For instance, as I find in the study, neither the PRD nor the upstream PRB can achieve the SSPs suggested socio-economic development as they need to share the same limited water resources. Therefore, regionalization of the scenarios narratives and assumptions through a participatory process with regional experts and stakeholders would further improve the robustness of regional water use projections. The recently implemented “river chief” system, which established a 4-level river manager system and appoints local governors as the “river chief” responsible for the protection and management of water resources in their administrative regions. The “river chiefs” will be held accountable for any water related damage in their region. As can be imagine, to achieve the sustainable development, or to avoid possible damage, local “river chiefs” must cooperate through a participatory process, seeking a multiple-win situation for all the regions within a river basin.