Conclusions and recommendations for further research

Andrew Bullock, Simon Mkhandi, Anthony Andrews and Denis Hughes

7.1 Project coordination and administration

Southern African FRIEND is a contribution to the Fourth International Hydrological Programme (IHP) of UNESCO, to the particular Programe H-5-5 ‘Application of methods of analysis using regional data sets’, and to the overall goal of IHP IV, being hydrology and water resources for sustainable development in a changing environment. Since 1991, Southern African FRIEND has become established as an international framework for the implementation of hydrological research relating to flow regimes in the region.

Based on this success, the programme should continue and contribute to the Fifth and subsequent phases of the IHP.

The programme has established a successtil profile with other international bodies, notably the World Meteorological Organisation, and has ensured complementarity of activities with the SADC Environment and Land Management Sector, and subsequently the SADC Water Sector. It is recommended that FRIEND should be assimilated more closely within the Integrated Water Resources Management Programme of the SADC Water Sector.

A Southern African FRIEND programme Coordination Centre has been established at the University of Dar-es- Salaam. Tanzania. A programme Steering Committee has been established and has met annually during this phase of FRIEND composed of national representatives from the eleven participating countries, UNESCO, SADC, the Coordination Centre and the research centres (involved in this first phase) at the University of Dar-es-Salaam, Rhodes University (South Africa) and the Institute of Hydrology ww

Coordination arrangements for the research themes have been established and implemented, with the River Flow Database Project coordinated by the University of Dar-es- Salaam and the Institute of Hydrology, the Spatial Database Project by the Institute of Hydrology, the Regional Surface Water Resources and Drought Assessment Project by the Institute of Hydrology and the University of Dar-es-Salaam, the Rainfall-Runoff Modelling project by Rhodes University and the Regional Flood Frequency Project by the University

of Dar-es-Salaam. Southern African FRIEND is, and should continue to be, represented in the UNESCO FRIEND International Coordination Committee by the Programme Coordinator.

Southern African FRIEND has been, and should continue to be, implemented as a loose affiliation of independently- fUnded projects with common and complementary goals, each benefiting from the existence of a common international database and from international collaboration.

There remains an open invitation to hydrological researchers concerned with flow regimes in Southern Africa to contribute to future Phases of the Programme. National IHP Committees within Southern Africa and in other countries wishing to contribute to the Programme are invited to increase awareness and the opportunities presented amongst national researchers of the FRIEND programme.

Chapter 1 has expanded upon the relevance of FRIEND to water resources management objectives, emphasising the contribution of research on flow regimes to different development, economic and environmental sectors. TO further advance the relevance of FRIEND in future phases, it is recommended that participating countries further define the links between river/water management objectives and flow regime measures.

7.2 Southern African FRIEND river flow database

The success in creating the river flow database by the FRIEND programme has represented a clear demonstration of the willingness of the eleven countries of Southern African to freely exchange hydrological data for the purposes of research. To facilitate the establishment of the international database, HYDATA has been established as a common software platform in each of the eleven countries for the archiving of hydrological data, thereby facilitating data transfer between countries in the region. Installation of HYDATA Version 3.2 1 has resulted in the upgrading of national hydrological archiving and processing software in nine of the eleven countries of Southern Africa. Over 50 staff from nine countries have been formally trained in the use of HYDATA, and additionally provided with a PC-

based self-help training module. It is recommended that National Hydrological Services and research institutions within participating countries consider the software requirements necessary to enable them to contribute to, and benefit from, products of this and future phases of the Southern African FRIEND programme.

A unified meta-data catalogue has been created with information on over 10,500 gauging stations which have been established within Southern Africa, as the basis for selection of suitable and available flow records. The FRIEND river flow database contains data from all eleven countries of Southern Africa. The database contains 676 time series of daily gauged river flow data and flood series, and contains 15,190 station years of data, with a modal length of 27 years per station. All data have been assembled on a single computer database at the Programme Coordination Centre. A new unifying gauging station numbering scheme has been developed and applied which accommodates and preserves many of the properties of the eleven national numbering schemes in operational use. The breadth of the assembled database, as the most substantial regional hydrological database yet assembled for Southern Africa, represents a unique source of information for large regional-scale or smaller international studies. Additional detail is provided by the nesting of catchments of different basin areas. It is recommended that participating countries and the River Flow Database project consider a periodic (every three or five years) upgrade to increase the number of gauging stations, particularly in areas with low densities of data, and to extend the period-of-record to include post- 199 1 data.

The database contains data series which have been validated as representing good quality data by the National Hydrological Services, and validation routines have been applied to remove gross errors. All FRIEND gauging stations have been categorised according to their suitability for flood, low flow and mean annual runoff analyses. It is recommended that participating countries investigate further both the quality control criteria applied to the selected time series (this could result in advice to the River Flow Database project to delete selected data series), based on consistent guidelines for quality assessment and the magnitude of artificial influences on the selected time series. The future interpolation of missing data in key flow series by patching would significantly enhance the usefulness of much of the data. The hmtre development of catchment similarity indices would assist in prioritising those data series (existing or new FRIEND stations) which represent data-sparse catchment types.

Access to the river flow database within FRIEND has been governed by data exchange agreements determined by the eleven participating countries, implemented by the

Programme Coordination Centre. Future access to the database would be enhanced by limited Internet (read and display) access to the FRIEND time series database. The constructed meta-data catalogues and the River Flow Database project require effective distribution to the National Hydrological Service in accordance with data exchange agreements. This distribution will assist hydrologists to implement research on the regional database within their host institutions.

7.3 Southern African FRIEND spatial database

The Spatial Database Project has assembled existing, and created new, databases of thematic information relevant to the controlling influences on flow regimes. It is recommended that future phases of FRIEND form appropriate links with global organisations (such as GRID- UNEP) and national organisations to ensure coordination of database creation and dissemination. Future production of an appropriate level of supporting documentation for the FRIEND databases will encourage their wider validation and application. It is absolutely critical that participating countries consider an effective upgrading of GIS capacity in order to receive and utilise the FRIEND spatial data.

A new integrated GIS coverage composed of national, hydrometric zone and gauged catchment boundaries has been created which, for the first time, is associated by the new FRIEND unifying station numbering scheme with gauging stations. This offers massive potential in disregarding national boundaries when deriving catchment- specific thematic information and for the presentation of hydrological information. It is recommended that improvements are implemented to enhance the representation of hydrometric zones in Angola, Mozambique and the incorporation of quaternary catchments of South Africa. Discrepancies between pre- published catchment areas and GIS-derived catchment areas for FRIEND gauging stations require investigation and resolution within the GIS coverage. ‘REGION-based’

routines require applications to polygons using national numbering schemes. Boundaries for any new gauging stations will require addition to the boundary coverage, with necessary amendments to the nesting algorithms.

A pre-existing lkm? Digital Elevation Model has been supplied by the United States Geological Survey for the Southern African FRIEND region. ARC/INFO hydrological modelling routines have been applied which identify flow directions from individual grid squares. This enables the accumulation of flow in a downstream direction, and the identification of upstream areas for any individual cell. This represents an invaluable tool for the future development

Chapter 7 : Conclusions and recornmendationsforfurther research

and application of hydrological design procedures in Southern Africa. Pre-existing digitised river networks have been assembled, created by NOAA EPA for the Southern African FRIEND region, and by the Department of Water Affairs and Forestry for South Africa (including Lesotho and Swaziland). It is recommended that future phases of the FRIEND programme stimulate cooperation with the United States Geological Survey to resolve errors in the DEM, and to assess the DEM performance in simulating catchment areas. A future region-wide structured river network database, either founded on DEM flowpaths or cartographic vectors, will contribute very substantially to river management objectives.

A Southern African-wide 0.5” grid-based time series (1961- 1990) of monthly rainfall was contributed by the Climate Research Unit (CRU)(IJK). Time series of rainfall data were provided by National Meteorological Services and Departments of Water Affairs, comprising 93 1 daily series and 3046 monthly series from eight countries. Monthly time series of Class A evaporation pan losses were made available for 66 sites. A Southern African-wide 0.5” grid-based Penman Potential Evaporation series was created from equivalent grids of the component micro-meteorological variables provided through UNEP. It is recommended that the FRIEND Steering Committee and the WMO advance the development and management by the National Meteorological Services of a region-wide time series database of daily rainfall data and monthly evaporation data, The climate database should be as comprehensive as possible in terms of historic data series to permit adequate temporal and spatial representation for hydrological (and meteorological) research at a Southern African scale, to be administered under appropriate data exchange agreements.

This initiative would substantially improve access for time series rainfall-runoff modelling to point climatic data and advance the development of region-wide grid-based monthly or daily rainfall and evaporation for the period 1960-1996 (or later).

The region-wide 30 ecosystem-type Olson vegetation classification was made available from the US Environment Protection Agency. A new region-wide grid-based coverage of percentage forest was generated from remotely-sensed NDVI (Normalised Difference Vegetation Index) data for 1986 and 1987, made available by NOAA. A new Southern African-wide 15’ x 15’ grid-based wetland coverage was created by sampling mapped wetlands, preserving up to 16 different definitions of wetland, floodplains and other water bodies as defined on national topographic map series. There is scope for future phases of FRIEND to enhance the categorisation of vegetation and wetlands in terms of dominant vegetation types and physiological structure (e.g.

canopy cover).

A digitised polygon coverage of the FAO Soil Map of the World was made available by FAO, with an associated transformation scheme (yet to be applied) which enables soil association labels to be converted to soil properties, such as texture and depth. A digitised polygon coverage of the SADCC (SADC but excluding Namibia and South Africa) Soil map was contributed by the SADC/FAO Food Security Unit. The future application of these coverages will be substantially enhanced by integrating products of national soil mapping from Namibia and South Africa into the existing SADC Soil map, and by applying the FAO guidelines for approximating soil properties. Relevant National Soil Agencies could be involved in such a process.

A new regional geology/hydrogeology coverage (excluding South Africa) has been created by digitising national maps, with integration and standardisation. Over 7,400 individual polygons have been labelled with five items that index the national lithology (as defined on national maps) a new regional lithological classification, which integrates the different national lithological schemes, aquifer type (as defined by the eight classes of the UNESCO hydrogeological scheme) aquifer productivity and aquifer yield. Equivalent coverages of geology and hydrogeology were made available by Department of Water Affairs and Forestry (but have yet to be integrated into the regional coverage). The future application of this coverage will be substantially enhanced by integrating products of national geological and hydrogeological mapping from South Africa (and new information from other countries). There remains much scope for combining the soil and geological/

hydrogeological coverages within a single hydrological response classification system.

Pre-published morphometric indices, such as catchment slope (S 1085) and stream frequency (STMFRQ) have been collated, where these have been calculated previously.

Future Phases of FRIEND could seek to ensure full and consistent derivation of morphometric indices.

Combination of the integrated boundary coverage with the other thematic coverages has been accomplished to create a relational database composed of single number and fractional areas of catchment characteristics for each of the FRIEND stations. The availability and collation of the thematic coverages offers significant opportunities for the retrieval of specific (e.g. rainfall) or combined (e.g.

hydrogeology in association with soils) catchment information for gauged catchments, hydrometric zones and countries, or (inclusive or exclusive) combinations thereof.

It was the original intention of the Spatial Database project to complete the construction of the thematic information on a timescale capable of providing consistent data to the three research programmes. However, the time requirements 153

in database construction meant that the thematic database was not completed prior to completion of the flood frequency and rainfall-runoff modelling research programmes. As a consequence. the spatial database has only contributed to the Regional Water Resource and Drought Assessment Programme. Nonetheless, the Spatial Database project has laid a very solid foundation .for supplying consistent thematic information in subsequent phases of Southern African FRIEND or in more regionally- specific developments of flood frequency or rainfall-runoff modelling.

7.4 Regional surface water resources and drought assessment

The Regional Surface Water Resources and Drought Assessment Project represents the first region-wide investigation of surface water resources and hydrological droughts for Southern Africa and has been directed towards five key issues; the spatial variability of mean annual runoff and regimes, temporal variability of annual runoff, base flow contributions to river flow, flow duration characteristics and estimation and regional drought assessment. The objective has been to advance methods to characterise the spatial and temporal variability of flow regimes and to provide guidance on their estimation for distribution of MAR, but which has significant limitations for flow estimation except where errors are known. It is recommended that subsequent phases of FRIEND evolve this capability for directly mapping gauged flow data through a more formal link between the GIS and time series databases to yield a visualisation tool for detecting gross errors in observed river flow data. In recent years, most countries have regionalised MAR within national boundaries. Acknowledging limitations introduced by the adoption of different methods and the distinction between natural and influenced MAR, nine national maps of MAR have been combined to construct a GIS coverage integrating current ‘best’ national estimates. Despite the Southern African region representing gross differences in climatic inputs, a hierarchy of regionally-based simple water balance models are not capable of explaining the variability of MAR.

Typical factorial standard errors are approximately 3.0. The overall estimation performance is restricted by the high variability of MAR for catchments with similar input variables (as demonstrated for a set of nine catchments in Malawi). The magnitude of different components of the water balance of Southern Africa is such that subtractive

methods, based on estimation of actual Eevaporation (AE), are generally beyond the current capability of actual evaporation estimation. Small catchments with different forest cover cannot be differentiated in terms of actual evaporation, Despite their lack of predictive capacity, such methods are invaluable in their application to characterise the spatial variability of water balance components. Noting that different countries have implemented different MAR estimation procedures, it is recommended that participating countries discuss the needs for, and merits of, a consistently applied MAR estimation procedure as a contribution to international river basin management. If such a product is deemed to be appropriate, then the creation of such a product could be advanced within the FRIEND framework, probably by a combination of regional surface water characterisations and the rainfall-runoff model’s (described in Chapter 6).

Further research work could be invested in seeking to explain the regional water balance of Southern Africa as a single geographic region, but, in parallel, greater effort should be directed towards the development of workable MAR estimation procedures in smaller geographic (but not national) regions, coordinated within the Southern African region as a whole.

A 0.5” grid based application of the probability distributed mode1 has routed a 196 1- 1990 time series of daily rainfall and evaporation through vegetation cover and soil texture parameter representations to simulate MAR at the Southern African region. Mode1 validation by comparison with MAR from FRIEND gauged catchments demonstrates a random tendency for under- and over-estimation. Recommendations have been made for subsequent improvement to the mode1 with regard to mode1 inputs (particularly rainfall), the representation of physical properties of catchments, runoff- generation processes, the representation of forest and wetland processes, and a move away from a grid to a region- based structure. Application of a soil moisture deficit and evaporation accounting model in Malawi has demonstrated that vegetation cover is an important factor in determining the spatial variability of MAR. The increase in runoff volume following a decrease of forest cover in Malawi of

13% during the period 1967-1990 is equivalent to 1 metre in the level of Lake Malawi. A preliminary analysis has demonstrated the use of the Southern African FRIEND data set in testing and improving the runoff prediction from global climate (SVAT) models. A demonstration based on the Kame catchment of Zambia illustrates the shortcomings of pre-existing parameterisations, and the considerable improvements that can be obtained by introducing observed MAR data. The capability to construct runoff accumulation products has been demonstrated by combining estimates of MAR with flowpaths constructed within the DEM and river basin coverage, including accumulated runoff volumes, identification of shared international rivers and categorisation of runoff generation zones in an international

Chapter 7 : Conclusions and recommendations forjrrther research

context. Wider application of such methods will contribute significant hydrological products to the SADC Protocol on Shared Watercourses.

Different MAR estimation methods have been discussed with regard to the estimation of monthly flow regimes.

Construction of a 4” X 4” visualisation ofrunoffand rainfall highlights key regime characteristics at a regional scale.

Temporal variability of annual runoff

Analyses have focused on the coefficient of variation of annual runoff (CV(AR)) as a single number index ofinter- annual variability. The relationship of CV(AR) with MAR demonstrates greater variability of annual runoff in catchments with low runoff - simply, catchments which

Analyses have focused on the coefficient of variation of annual runoff (CV(AR)) as a single number index ofinter- annual variability. The relationship of CV(AR) with MAR demonstrates greater variability of annual runoff in catchments with low runoff - simply, catchments which