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Summary Watermanagement Exam
Summary of the chapters 5,7,9,12 of the book Water Resources_ An Integrated Approach-Routledge (2013) by Joseph Holden. This is part of the exam of watermanagement
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Seminar 1: Introduction to Water ManagementChapter 7: Water and Health
Summary
Balancing water demand and supply, and protecting or enhancing environmental qual-
ity at the same time, is challenging under conditions of growing uncertainty. Water re-
source development takes a long time, and so demand forecasting is required. Such
forecasting requires a strong demographic element, and the information base on wa-
ter-demand fluctuations at the household level is weak. Water supply also needs to ac-
count for a range of other demands on resources, including leakage, theft, operational
use and emergency use. Water efficiency in both domestic and industrial arenas has a
significant role, but sophistication in precisely what efficiencies are promoted is vital.
Decisions need to be robust and to reflect uncertainty, if they are to contribute to a re-
silient system.
A Introduction
Demand for water grows because of demographic change, increased needs for
agricultural produce, urbanization and supply of manufactured products.
Middle East and North Africa: areas with poor water resources, and large reductions in
water resources over past 60 years.
In for example Germany, technological advances drives reduce demand through water
efficiency, reduced activity of water-consuming industry have resulted in declining
demand.
Water demand management involves: large-scale water resource inventories
(groundwater and surface water accounting, usage rates, replenishment rates) to try
to secure resources to meet demand. More importantly: involves working with people
to alter attitudes and behavior so as to reduce water demand.
B Sources of demand
Demand of water varies depending on the nature of the water involved —> potable,
flood, urban wastewater.
Demand for raw water different from demand for potable water.
Raw water demands: irrigation requirements for agriculture (major), potable
consumption (minor), industry, abstraction (in-stream use), power generation,
navigation for shipping.
Key point is to understand how the demand for water interacts with energy (biofuels)
and food requirements and circumstances.
Implicit requirement: must be sufficient water to dilute pollutants.
Water demand in stream is interconnected with multiple off stream uses via
abstractions and discharges that occur in river systems.
C Measuring current potable demand
1 Water metering
Demand is how much of a good a population will choose to buy for a set price. Water
is more problematic resource to consider in that style because:
1. It is not a matter of pure choice, as water is essential to life.
2. Demand is not always directly measured but must often be estimated. Universal
water metering are dumb meters that at different times and themselves
, representing an aggregation of different time periods. Many homes have no water
meter and pay single charge based on size/value of house.
2 Demand estimation
2 main approaches to demand estimation based on either domestic consumption
monitors or district meters
2.1 Bottom-up
Aggregating estimates of demand made at the individual household level.
Domestic consumption monitor or domestic water use survey: sample of about
2000 consumers who pay on a standard tariff. But not representative cultural
water-use differences. Also bias for water survey, because people choose to
enter it.
There is a range of known biases in domestic consumption monitors (DCM)
Self-selection: when water company wishes to create a DCM the people who
choose to join are self-selected. They may join for a reason.
Staff: company may encourage own stop to join, but they are more informed
and likely to behave correctly.
Exclusion: not everyone feels ale or is allowed to join a survey.
Financial advantage: compensation for time it takes to complete forms and
record information is for some an income source or for supplemental income.
Hawthorne effect: People tend to make an effort to perform in the direction
expected (unconscious).
The challenge of demand analysis is to determine the overall direction of each
bias and to allocate an estimate of the extent of bias so that a correction can
be entered into the final demand estimate. The sample information on which to
calculate per capita demand could have drifted at least 25% into error due to
the requirement in countries to report the household water demand and
average per capita demand, but household sizes change often. So for bottom-
up approach water supply bodies must resurvey on at least annual basis.
Parts of the table for ware-demand analyst: Household consumption, number of
residents per capita and water demand. The per person demand can be
determined by use of OVF calculations (ownership, volume and frequency),
sometimes known as micro-components (toilet flushing, tap use etc.).
2.2 Top-down
Disaggregating from an area measurement
Top-down demand estimation is derived from the system of area meters, the
water in a distribution system is derived from. The meters measure total water
passing through the pipe, irrespective of final use. It is the sum of many
demands in large area.This makes the determination of household demand
more complex and less direct.
If the values of bottom-up and top-down demand estimated lie within 5% of
each other little further action is deemed. If they lie outside this band, some
form of outcome reconciliation is required which may either be an arithmetical
or an investigative correction.
, D Trends in water demand
Water is driven by population, lifestyle and economy. It is trending upward, for the
next 20 years. Thereafter there is uncertain in the population forecasts. For developed
countries irrigation is
major water demand.
More industrialized
countries, commercial
and domestic water
requirements are more
important. By 2030 a
major gap between
water resources
demanded and
sustainable resource
availability is expected.
Without significant
interventions there will
be water shortages.
Typically in the
developed world, this
might be addressed by demand reduction and resource development. But mostly the
last one is the only option. But exploitation does not always exist and is troubling due
to drought, crop failure and conflicts about water access.
Forecast of OECD: population suffering from severe water stress will rise to 3.9 billion
by 2030.
OECD definitions:
Water stress: water resource falls below 1700 m^3 per person per year.
Water scarcity: resource falls below 1000 m^3.
Absolute water scarcity: occurs when resource falls below 500 m^3
UN Water for Life definitions:
Water scarcity is the point at which aggregate impact of all users impacts on the
supply or quality of water under prevailing institutional arrangements to the extent
that demand cannot be satisfied fully. So scarcity occurs when water resource
availability is significantly below that which we have become used to and which we
have anticipated being available in the future.
Since water scarcity is addresses the balance between water resources and
population, there is not only focus on desert countries.
Demand differs with countries, these with same level of economic development can
have different water demands due to average household size, propensity to live in
flats (EU) and grassed lots (USA) and difference in data collection (leakage included or
not)
As the water price increases above $3 per m^3 the gap between the highest and
lowest water use diminishes and the demand is fairly consistent around the 50 m^3
per capita per year. Canada, US and Australia have relatively high water use.
Water demand by industry can be raw and potable water. The water demand of
specific industry is driven by outputs which can be measured either by material
finished product metrics, by sales or by the labour force employed. This is modified
slightly by water price, water stress, and regional soil moisture deficit.
In the future, water-saving strategies of each industry need to be determined which
depend on technologies thought to be available and rate of uptake of technology.
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