Recommendations and conclusions

13.1 Introduction

In both developed and developing countries, there is increasing pressure to improve the reliability of water resources schemes and enhance ecosystems degraded by overabstraction and pollution. Both surface water and groundwater resources are under greatest pressure during low-flow periods, and with population growth and climate and land-use change these pressures will increase. It is thus essential that water resources schemes be designed and operated so that people’s livelihoods and the ecosystems on which they depend are enhanced. This can be achieved only by developing and dissemi-

nating operational techniques based on a thorough un- derstanding of drought processes, good-quality hydro- logical data and analytical techniques appropriate to a wide range of environments. This chapter makes a number of recommendations for improving abilities and reducing the uncertainty in predicting and forecas- ting low flows in three areas: data collection, operational applications and capacity-building.

13.2 Data

Estimates of the frequency of low flows require long, preferably unbroken, time series, while the need to make estimates at sites without data is reduced if there is good spatial coverage. Chapter 3 describes a number of techniques for processing, controlling the quality of, and disseminating hydrological data. In some countries these methods are well established; but, in many parts of the world the resources allocated to en- vironmental monitoring are inadequate and both the volume and quality of data are in decline. The highest priority is therefore to ensure that there is a long-term commitment over several decades to increasing the resources allocated to data collection and disseminating good practices, particularly, but not only, in develop- ing countries. Networks need to be expanded, data processing and quality control improved, and diffe- rent environmental datasets must be integrated into geographic information systems and freely dissemi- nated.

It is anticipated that there will be continued improve- ments in sensors, data loggers and processing soft- ware. Advances in remote-sensing and low-cost sensors for measuring water levels should improve the availa- bility of data from large rivers and lakes, particularly in remote locations. The spatial resolution, global cov- erage, measurement frequency and record length will continue to improve along with the remote-sensed measurements of land use and snow and ice. This will have direct benefits in estimating the impacts of land- use change in large basins and that of deglaciation on dry-season flows.

In many catchments, the dominant impacts on hydro- logy are the artificial influences caused by the con- struction of reservoirs, direct river abstractions, ground- water pumping, power generation and urbanization. There is a need to improve the availability of information

on the location, volume and timing of these influences using direct measurements for the dominant impacts and estimation procedures for the large number of minor influences. For the improved operation of water re- sources, it is essential to have access to data in real time to make decisions on, for example, the operation of a hydropower scheme or the control of abstractions. The next decade will see continued advances in the

real-time dissemination of precipitation, stream flow, groundwater level and reservoir data, as well as the synthesis of this data through regular reports on the current status of the low flows and flow forecasts. The increased use of the Web as a platform for data dissemi- nation will improve access to information and its exchange between environmental protection agencies and power and water utility companies; the general public will also benefit.

13.3 Operational applications

Where there is adequate data for understanding low- flow processes or for hydrological design, this should always be used in preference to a predictive model. However, on many occasions data are absent or in- adequate. In these situations, it may be necessary to

130 ReCommenDatIons anD ConClusIons

develop a hydrological model, for example, to esti- mate low flows at an ungauged site or to predict the impact of land-use change.

Chapter 9 describes different regional hydrological models ranging from simple empirical relationships to more complex multivariate models. The key appli- cation of these models is to estimate the frequency of low flows at sites for which flow data is not available. The main limitation on their further development is the requirement of good-quality hydrological data for model development and calibration and the absence of the most appropriate catchment descriptors. All basin properties must be in digital form and, where necessary, new descriptors need to be developed. Although it is recognized that hydrogeology is a key variable in controlling low-flow response, it is rarely incorporated explicitly in regional low-flow models. It is also neces- sary to improve estimates of model uncertainty by testing the model on a subset of catchments not used in calibration.

Although the science of stream ecology is outside the scope of the Manual, the estimation of low flows is often a key issue in river-flow management. One of the most important reasons for improving our under- standing of river ecosystems is to develop instream flow models for improved river management, particu- larly for minimizing the impact of river abstractions on the abundance and diversity of stream biota. Very rapid assessment techniques where the ratio of an ab- straction to the natural low flow is very low are still in demand. Although simple low-flow statistics have traditionally been used, the availability of national field programmes and associated databases describing channel geometry and substrate combined with flow information should lead to significant advances in rapid assessment techniques.

There is considerable opportunity for improving the transfer of existing knowledge from the research to the operational community. For gauged locations, it is essential that software be available to analyse the range of low-flow indices described in this Manual, with ta- bular and graphical outputs in an appropriate form for the decision-making and reporting of the operational agencies. To estimate flows at ungauged sites, existing regional models must be integrated with digital data- bases of catchment descriptors.

This may require major national digitizing program- mes to convert existing maps into digital form or the

bringing together of disparate databases of meteoro- logy, hydrogeology, soil surveys, river networks, land use and topography.

There have been considerable advances in hydrological modelling over the last two decades using different types of hydrological models operating at a range of spatial scales. Most of this research has focused on reducing the uncertainty of model prediction based on the calibration of single catchments or small subsets of catchments. One of the most important priorities is to build on this expertise to regionalize monthly and daily continuous simulation models. Using inputs of daily precipitation and evaporation, it will then be feasible to generate long periods of daily flows at ungauged sites, extend short records and predict the impact of land-use change or the sensitivity of low flows to climate variability. The regionalization of these models will enable operational hydrologists to carry out these tasks for all river reaches within a region.

Hydrological design is rarely required in sparsely po- pulated pristine catchments. Conversely, most hydro- logical problems arise in densely populated catch- ments and in areas with the greatest pressures from competing water users. These catchments, which have very complex patterns of water use, are rarely studied by the research community. There is an urgent need for the improved monitoring and modelling of these artificial influences. Although some impacts are relatively simple, for instance, the effect of a sewage discharge on low flows, others are more complex, such as the impact of groundwater pumping or urbani- zation. A holistic approach to integrated catchment management must be adopted in contrast to the histo- rical approach of considering issues separately for each water industry sector.

At the global level, there is a need to advance opera- tional design and forecasting in developing countries. In mountain environments, there is a need to predict the long-term impact of deglaciation on dry-season flows. This is of particular importance in the Himalayas and the Andes, where low flows derive primarily from glacial meltwater and are critical in the dry season for agricultural and drinking water.

Advances in operational hydrology will be accelerated if long-term partnerships can be established between the user and research communities. This enables the operational requirements to be clearly specified before a research programme is initiated. It is important that

131

the final product be compatible with the available data, the skills of the organization and its policy objectives. Normally, research will be transferred through software, which must be supported over several years so that de- cision-support systems can be refined according to ad- vances in the underpinning research.

13.4 Capacity-building

The management of low flows in extreme droughts puts considerable strain on individuals and organizations if they are not well prepared. In the past, the primary concern was to develop a strong physical infrastructure, which was deemed necessary to cope with the compe- ting demands of different stakeholders. Although infra- structures may have been appropriate to make optimal use of the available and even decreasing water resour- ces, infrastructure management was often inadequate, such that systems were far from sustainable and the ser- vices provided deteriorated unacceptably. Thus, institu- tional capacity and detailed planning are crucial for good low-flow management. A key component of this is to ensure that, before an extreme event, organizations have the necessary tools and experience to analyse and interpret low flows. There is a need for a strong under- lying knowledge base (as reported in the previous chap- ters) and the corresponding capacity of managers to act. In particular, managers have the responsibility to plan,

manage and use the available infrastructure and to ensure proper governance of the water sector. This, however, requires appropriate knowledge resources and the in- volvement and attention of all stakeholders, from the government level right down to individual water consu- mers.

Capacity development is the process by which indivi- duals, organizations, institutions and societies de- velop abilities (individually and collectively) to perform functions, solve problems, and set and achieve objec- tives (UNDP, 1997; Lopes and Theisohn, 2003). This involves management in the areas of resolving con- flicts, dealing responsibly with change, coping effec- tively with institutional pluralism, encouraging com- munication, ensuring that data and information are collected, analysed and shared, and creating the neces- sary conditions for knowledge generation, sharing and transfer. Three levels of capacity development can be identified (Figure 13.1), namely, the individual and institutional levels embedded in the appropriate enabling environment (van Hofwegen, 2004). Without capable individuals who are both competent to

think through the issues associated with low flows and have the authority and ability to act responsibly in a collaborative manner, little can be achieved in mana- ging the critical situations that may arise. This is a hu-

Figure 13.1 The three levels of capacity development (World Water Assessment Programme, 2006; adapted from van Hofwegen, 2004) ReCommenDatIons anD ConClusIons

Individual