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CLOSE THIS BOOKHandbook for Agrohydrology (NRI)
Chapter 1: Introduction
VIEW THE DOCUMENT1.1 The role of hydrology in agriculture
VIEW THE DOCUMENT1.3 Project planning and practical problems

Handbook for Agrohydrology (NRI)

Chapter 1: Introduction

1.1 The role of hydrology in agriculture

Agrohydrology can be regarded as the study of hydrological processes and the collection of hydrological data, aimed at increasing the efficiency of crop production, largely by providing beneficial soil moisture conditions. However, the influences on the production of runoff and the ways that runoff affects the environment within which crops grow are very diverse and agrohydrological study, of necessity, also includes the collection of information on climate, soils, vegetation and topography. Rainfall amount and its spatial and temporal distributions determine the quantity of water that reaches the land's surface. Temperature and humidity, the type, amount and distribution of vegetation cover determine what proportion of this water re-evaporates. Vegetation, soil conditions and topography determine how much water infiltrates into the soil, how much runs off the land's surface and where it goes. It is the interaction of these complex processes and the volumes of runoff that these processes produce that form the core research of agrohydrology.

Hydrological practice has been developed to its greatest extent and sophistication in the provision of water resources from large catchments, usually for industrial and domestic consumption. Historically, hydrological practice has had a limited role to play in agriculture even where large-scale irrigation schemes have been undertaken, because civil or agricultural engineering expertise has usually taken a dominant place in such circumstances. But with the increasing interest in improving poorly developed and more marginal regions of agricultural activity, where large capital investment is uneconomic, a thorough understanding of the hydrological conditions that prevail has become essential. This understanding is particularly important where agriculture is a subsistence activity, or where water harvesting is proposed to improve agricultural production. Knowledge of the hydrological environment is necessary to determine whether or not opportunities to create optimal soil moisture conditions exist, and how these opportunities can be exploited.

Also, the understanding of the hydrological environment links together with other important environmental issues: the removal of natural vegetation, soil erosion, flooding, drought. The influence of hydrological conditions on farming practice and farming systems is substantial, and in the case of water harvesting, the availability, timing and volume of surface runoff will be critical to success or failure.

The actual techniques and methods that are used to collect information for agrohydrological study are, in general, very similar to those used in more orthodox hydrological field practice and the transfer of technology is not a problem, but there are some differences. These differences may be summarised as follows:

- the catchments from which runoff is measured are usually smaller.

- runoff peaks and volumes are also usually small. This often necessitates the modification of otherwise standard equipment.

- often, studies concentrate upon the particular conditions under which runoff is produced and particular conditions may even be imposed upon a catchment. The use of "natural" catchments is not common.

- it is often necessary to study many replicates of catchment types.

- particular conditions of climate (especially rainfall) and catchment may have only a very localised extent.

- a close connection with farming practice will be desired.

- historical hydrological (and sometimes other) data will be limited.

- methods of analysis of data are identical, but the shortness of records often imposes severe constraints.

The aim of this guide is to show which hydrological factors are important and how they can be measured, so that any opportunity for improving the water supply to crops can be taken. The core interest of the guide is runoff, the surface flow of water and the rainfall and catchment conditions that cause it.

1.2 Summary

This book is directed at agricultural projects whose staff do not have the specialised skills of the hydrologist and at hydrologists whose experience in the agricultural field is limited. It is aimed especially at those working in developing countries, where resources will be limited and where it is essential to put the right equipment in the right place, in the right way. Projects usually have a very short life-span compared to the time it takes to collect a comprehensive set of data and a season that does not yield information that can improve the quality of future decisions is, effectively, a season lost.

The Contents of this Handbook

A deliberate attempt has been made to bridge the gap that is so commonly found between textbooks and guides to field practice. It is often the case that textbooks discuss in detail the theory of hydrology, but give little or no explanation of how this theory is applied to hydrological work. The material may make sense in isolation, but it often cannot be translated into real field activity. For obvious reasons the authors of texts do not select limited data of dubious quality for illustrative examples, but this is exactly the kind of data that are found frequently when work is undertaken at the project level. Similarly, practical guides often leave the reader with no accurate background to the theoretical basis upon which their research is founded. When research moves away from its theoretical basis, to accommodate the realities of everyday life, it is important to know exactly where it stands and whether or not the links with sound theory have been stretched too far.

There are three main components to this handbook. These are chapters 2, 7 and 8 which cover Runoff and its measurement, Water Harvesting and Field Structures, and Data Analysis, respectively. The other chapters are important, but these three cover the fundamental aspects of agrohydrology. Equipment used for the collection of data is essential to the successful acquisition of agrohydrological knowledge. Its manufacture, installation and maintenance are covered in depth. A breakdown of the main topics of each chapter is given below.

Breakdown of Chapters 2 - 8

Chapter 2: Measurement of Runoff
- theoretical estimates to help in the selection of appropriate equipment
- hydrometrics/ runoff controls, both natural and artificial
- measurement of hydrological variables
- equipment descriptions
- equipment manufacture? installation and maintenance

Chapter 3: Sedimentation Data Collection
- soil erosion and methods of estimation
- total sediment and suspended sediment measurement
- equipment
- laboratory analysis of water and soil samples

Chapter 4: Rainfall and Meteorological Data Collection
- equipment descriptions for all major meteorological variables
- installation and maintenance
- siting and operation
- raingauge networks

Chapter 5: Soils and Soil Moisture
- soil classification
- soil textures
- methods of determining soil moisture
- infiltration
- equipment

Chapter 6: Catchment Characteristics
- natural vegetation
- catchment size, land slope, topography
- field orientation
- geology and other influences

Chapter 7: Water Harvesting and Structures
- types of on and off field systems
- results from research examples of these systems
- design criteria. channels and waterways
- practical aspects of laying out fields/ agricultural engineering

Chapter 8: Analysis of Data
- runoff data, non-statistical analysis
- statistical analysis, theoretical distributions of data
- rainfall and other meteorological data
- rainfall intensity
- rainfall/runoff relations
- evaporation and evapotranspiration


The list of books and papers given below has been limited to those which bear directly on the text of this handbook and most of them should not be difficult to obtain. The range of reference material on hydrology and agrohydrology is extremely comprehensive but it is recognised that some field workers may find difficulty in obtaining such material. Some of the references below are orthodox textbooks that deal largely with theory, while others are field manuals or research papers that report experience at first hand. It is hoped that this mixture of theory and practice will provide a good basis from which research can be undertaken? while at the same time allowing researchers to follow their own preference toward particular reference material.

A generalised computer program for the solution of the Penman equation for evapotranspiration. Chidley, T R E and Pike, J G, 1970.
Journal of Hydrology 10 (1970): 75-89

A rapid method of computing areal rainfall. Chidley, T R E and Keys, K M, 1970.
Journal of Hydrology 12 (1970): 15-24

Agrometeorological crop monitoring and forecasting' FAO Plant Production and Protection paper 17, 1979
FAO, Rome

Applications of remote sensing to hydrology, S T Miller, 1986
PhD Thesis, University of Aston, Birmingham, UK

Annual floods and the partial duration series. Langbein W, 1949
Transactions of the American Geophysical Union, 30: 878-881

Arid zone hydrology. FAO Irrigation and Drainage Paper 37, 1981
FAO Rome

Climate of Botswana, part II Elements of climate. Bhalotra, Y P R, 1984
Department of Meteorological Services, Gaborone, Botswana

Effect of slope and plant cover on runoff, soil loss and water use efficiency of natural veldt. Snyman, H A and Van Rensburg, H A, 1986. Journal Grassland Society of South Africa 3,4: 153-158

Field manual for research in agricultural hydrology, 1979
USDA Agriculture Handbook 224. Washington DC, USA

FAO Soils Bulletin no. 1(), Physical and chemical methods of soil and water analysis 1970.
FAO Rome

Flood studies report, 1975 Natural Environment Research Council, UK

Field directors handbook, Oxfam 1985
Oxford University Press, Oxford. UK

Handbook of applied hydrology, 1964. Ven Te Chow (Editor in chief) McGraw-Hill, New York

Hydraulics of runoff from developed surfaces. Izzard, C F, 1946 Proceedings of the High Resolution Board, 26: 129-150

Hydrology for engineers, 1985. R K Linsley, M A Kohler and J L H Paulhus McGraw-Hill, New York

Hydrology for soil and water conservation in the coastal regions of North Africa United States Department of Agriculture Soil Conservation Service, 1974. Washington DC, USA

Instructions and tables for computing potential evapotranspiration and the water balance. Thornthwaite, C W and Mather, J R, 1957. Drexel Institute of Technology, Publications in Climatology Vol X, No 3.

Irrigation principles and practices, 1962. O W Israelson and V E Hansen John Wiley and Sons, New York

Land husbandry manual, 1977 Ministry of Agriculture & Natural Resources, Lilongwe, Malawi

Land and water management project ODA/SACCAR. Annual Reports, 1989 - 1992 Natural Resources Institute, Chatham, UK

Land and water management project. Hydrology final report, Miller S T, 1994 Natural Resources Institute, Chatham, UK

Measurement and prediction of actual evaporation from sparse dryland crops, Wallace, J S, Gash, J H C, McNeil, D D, Sivakumar, M V K. 1986. Report on project 149. Institute of Hydrology, Wallingford, Oxfordshire, UK

Meteorological observers handbook 805, 1969

Microtopography and agriculture in semi-arid Botswana 1. Soil variability, Miller S T, Brinn, P J, Fry G J and Harris D, 1994. Agricultural Water Management (in press)

Prediction of variation in grassland growth in semi-arid induced grassland. Dye, P J, 1983. PhD Thesis, University of Witwatersrand, Republic of South Africa

Predicting rainfall erosion Losses, 1978
United States Department of Agriculture report 537

Principles of hydrology, Ward, R C. McGraw-Hill Ltd, 1975
London, UK

Probability and statistics in hydrology, V Yevjevich
Water Resources Publication, 1972
Fort Collins Colorado

Probability and statistics for engineers and scientists. Walpole, R E and Myers, R D Collier Macmillan, 1985, New York, USA

Rainfall-induced runoff computed for fallow fields, Hauser,V L, Hiler, E A, 1974. Soil and Water Division Paper 73:2520, ASAE.

Remote sensing and image interpretation, 1979. TM Lillesand and R W Kiefer Wiley and Sons, New York

Soil conservation, Elwell, H A
College Press, 1986. Harare, Zimbabwe

Soil water balance in the Sudano-Sahelian Zone. IAHS Publications, 1991 Institute Of Hydrology, Wallingford, Oxfordshire UK

Soil and Water Conservation Engineering. G O Schwarb, R K Frevert, T W Edminster, K K Barnes Wiley and Sons 1981, New York

Stochastic considerations in optimal design of a microcatchment layout of runoff water harvesting, Oron. G and Enthoven, G. 1987. Water Resources Research 23:7:1131-1138

The quantification of runoff and factors influencing its production, Miller, S T and Veenendaal, E M,1990. Proceedings of the Land and Water Management Research Programme Scientific Workshop, Gaborone, Botswana

Three years experience with an on-farm macro-catchment water harvesting system in Botswana Carter. D C and Miller ST 1991. Agricultural Water Management 19 (1991) 191 -203

Time domain reflectometry in soil science: theory, operation and use. Robinson, D, 1993. Institute of Hydrology, Wallingford, Oxfordshire, UK

User's handbook for the Institute of Hydrology's neutron probe system, 1981. Institute of Hydrology, Wallingford, Oxfordshire, UK

Vegetation management guidelines for increasing yields in a semi-arid region: an Arizona case study, Fogel M M, Report of the School of Renewable Natural Resources, University of Arizona, Tucson, USA

Water harvesting for plant production. Reij, C, Mulder, P, Begmann, L, 1988. World Bank Technical Paper 91. Washington DC, USA

Equipment Cost Lists

At the end of each chapter, there is a list of basic equipment and 1993 prices in US $. The cost of scientific equipment is often surprisingly high and although these prices may soon be out of date they provide a useful basis for early planning until current prices can be obtained, a process which can take weeks or even months. Below are the names and addresses of a number of UK manufacturers and suppliers of scientific equipment. This should be of use when researching equipment prices and availability.

Note that inclusion in this list does not confer an' recommendation by NRI




Casella London Ltd

Regent House, Wolsley Road,


Kempston, Bedford MK42 7JY

England. (Fax: 0234 841490)

ELK International Ltd

Eastman Way, Hemel Hampstead


Herts. HP2 7HB, UK.


(Fax: UK + 0442 252474)



Mon Plaisir 25, Postbus 373 4879 AK


Etten-Leur, Nederland.

(Fax: 01608 33181)

Schonbergstrasse 47? D-7302

Ostfildern 4, Deutschland

(Fax: 0711 457 09 51)

Smail Sons & Co Ltd

Unit 1, St. Andrews road,


Glasgow G41 lPP. U


(Telex: 041 429 4429)

Vector Instruments

115 Marsh road, Rhyl, Clwyd

Wind monitoring

LL18 2AB. UK.

(Fax: UK + 0745 344206)

Delta T Devices Ltd

128 Low road, Burwell, Cambridge




(Fax: UK + 638 743155)

Loggers & Software

Valeport Ltd

Unit 7, Townstal Industrial Estate,


Dartmouth, Devon TQ6 9LX. UK

(Fax: UK + 0803 834320

Soil Instruments Ltd

Bell lane, Uckfield, East Sussex,

Soils and Geotechnical

TN22 1QL. UK

(Fax: UK + 0825 761740)

Didcot Instrument Co Ltd

Unit 14, Thames view Industrial Park,


Abingdon, Oxon, OX 3UJ. UK

Soils & Neutron Probe

(Fax: UK + 0235 522345)

Appendices to Chapters

For ease of reference and where appendices are appropriate, the material is placed at the end of each relevant chapter and the sequential page numbering of the chapter is continued. The page numbers of the appendices are listed in the Contents section.

Computer Models

A very short list of "off the shelf" models and database systems, that can be used for catchment and agricultural flow simulations is given below. There are great difficulties in providing such a list: very many research institutes, university departments and private companies have developed or are developing models based on some or all of the physical processes involved in rainfall/ surface flow/ soil moisture/ crop/ natural vegetation/ groundwater recharge, etc., to determine various water balances. Some of these models will be relevant only to specific research purposes, while others will be intended for general release, to be used in many different circumstances. To keep track of all of these developments is an impossible task. It is recommended therefore, that enquiries for details of models for field projects should be directed to the funding organisations of such projects. These organisations will be in a good position to contact research organisations and national institutes for details and may indeed be funding the development of water balance models themselves. Local organisations (Water Authorities, Ministries of Agriculture, etc.) may also be able to provide useful information on any models that have been developed or modified for use under local conditions. The following models and databases are presented because they are (mostly) in widespread use, and they have been used and tested for some years. The programs are not suitable for use with small runoff plot data, but are designed to be used with a p.c. Enquiries need only be directed to one organisation, the Institute of Hydrology, Wallingford, OX10 8BB, UK.

"HYDATA" is a hydrological database and integrated analysis system, best suited for catchment purposes. Currently it is used in 15 overseas countries. It stores station data (location, name etc.), stage and rating equation data, flows, rainfall and meteorological information. It has been developed to be compatible with the WHO's meteorological database, CLICOM via a transfer utility "HYCOM". Analysis gives comparison plots (eg double mass curves) or time series (eg hydrographs), flow duration and low flow information. Current price £5,000.

"HYFAP" is a frequency analysis and modelling package developed for use with extreme event information (eg annual maximum flows) for the prediction of magnitudes and return periods. Various distributions and fitting methods (see chapter 8) are available. Data can be transferred directly from HYDATA using an optional utility package "HYDOUT". Current price £495.

"HYRROM" is a relatively simple conceptual, deterministic rainfall/runoff model. Rainfall is routed through an interception and soil store, with evaporation and transpiration deducted. Runoff is given after losses to groundwater are accounted for, though groundwater contributions are added after a time delay. The model can be manually calibrated. It is compatible with HYDATA. Current price £825.

"Micro-LOW FLOWS" is a modelling program that incorporates the findings of the Natural Environment Research Council's Low Flow Study. Catchment characteristics are used to provide mean, 95 percentile and mean annual minimum flows; low flow frequency and flow duration curves. Current price £1100.

"Micro-FSR" is a software package for estimating design flood flows and probable maximum precipitation, using statistical modelling techniques (see chapter 8). Current price £995.

"SWIPS" is a soil moisture quality control, processing database for data from neutron probes, capacitance probes and tensiometers, and is run under Windows 3.1 operating software. Current price not available.

* For updates of packages and prices contact IOH. Bona fide research organisations/projects can purchase at large discounts.

1.3 Project planning and practical problems

This handbook assumes that work is being undertaken in developing countries and usually, though perhaps not always, will be implemented through a project with a finite lifetime. It is important to consider briefly, the manner in which projects are formulated and evaluated. Project staff should be aware of how and why projects have been devised and funded, and understand the work that has gone into developing the project proposals. Their own experience may be invaluable for future proposals for project development.

Projects have a finite life, but should seek to attain their goals and leave behind continuing benefits that come from the successful integration of new developments; technical, economic and perhaps social. Technical staff have important contributions to make in these areas, to both current activity and future planning, but it would be naive to believe that technical improvement and social benefits are the only aims of funding agencies. Policy and administrative considerations are often paramount and it is essential that technical assessments should be thorough and realistic.

Proposals and Planning for Projects

Project proposals are the first tangible evidence of possible future activity. They collect together ideas generated by the previous work and experience of individuals and organisations and will pass through many different stages of development before final acceptance or rejection. Because of this, project proposals may develop over a long period of time and it is important that their relevance is continually assessed. It is also advantageous, and in the case of most projects essential, that in addition to technical and logistical enquiry, the specialist skills of sociologists and economists be applied at the earliest stage of any proposals, to define the possible consequences of implementation. It is also important to remember that each funding agency will have its own individual character and particular spheres of interest and experience.

A list of basic conditions that project proposals should fulfil is given below. These address the structural and material content of proposals and do not consider any of the important social issues that can undermine the success of any technically feasible project. Project proposals should take into account:

Clearly defined aims and objectives

These should explain precisely the long and short term goals that the project seeks. They should be agreed upon and documented prior to any implementation. In some cases they may be limited to the stages of technical implementation and their results, in other cases it may be necessary to include the socio-economic effects that are expected and the development of the activities of the project, in the light of these effects.

Institutional framework

This will identify the interested parties and clarify the position that the project occupies between them. The responsibilities of the organisations involved and the financial, staffing and logistical support that a project receives, should be explained in detail.

Lines of communication between Project, Donor, Recipient Organisation and Participants

These are often complex, but vital to the success of a project. Misunderstandings may lead to a lack of amicable cooperation. They provide essential conduits for reporting, review procedures and information, and keep everyone involved aware of the progress of work and need for revision.

Reporting Procedures

Strong lines of communication are useless without defined reporting procedures. If these are well established within project proposals, it is not easy to neglect them, even when a project is running and day to day tasks have a more immediate attraction.

Evaluations and Reviews, both internal and external

Project proposals (and activities) are not immutable and a flexible approach is essential. Conditions change continually and it is not possible to design, implement and complete a project without considering improvement as experience is gained. Review procedures are important to ensure that sensible assessments of progress are made and to initiate discussions on alternative courses that may be followed. Both internal and external reviews should be timetabled, with at least one major review allocated to a project at the most suitable stage of development. The difficulty here is to balance the timing; it should be neither too late to be of use, nor be too premature to review sufficient material. Short term reviews, perhaps annual internal reviews, can be made available and help in selecting appropriate timing, but much will depend on the nature of the project and its duration. The nature of the review bodies should be stated, as should to whom they will report and their constituent members.


Funding may sometimes be contentious, sometimes easily agreed upon. In terms of project success, it is often the distribution of funding that causes problems rather than (within reason) the amount. It is usually most convenient for funding agencies to disburse an evenly spread level of funding. This allows consistent administrative procedures and easier future budget planning, but it is rarely appropriate for the efficient running of projects. Project capital investment expenditure is relatively high at first, gradually decreasing over the project life. Conversely, funds for employing local staff, equipment repair, vehicle maintenance and fieldwork will become greater as the project grows. Funds for training tend to peak during the mid and final term when staff have sufficient experience to require enhanced expertise and suitable courses have been identified. Problems can arise not only from the varied levels of funding needed in each case, but also because each may be obtained from different areas of fiscal responsibility within the funding organisation. It is clearly to everyone's advantage to assess realistic levels of funding in detail, relate them to the stages of the project's life and identify remedial procedures, should these be necessary. The responsibilities of all organisations concerned with supporting the project, should be clearly stated.

Long-term Obligations

The project proposals should place the role of the project clearly within the framework of past activity and where long term obligations are planned, agreements on these should not be postponed nor over looked. The manner in which the results of the project fit into the social and institutional framework of the host country and whether or not they can be maintained, should be assessed. Projects usually become self funding over a timetabled period, but it is easy to overestimate local sources of support where attention is distracted from problems of future funding by the overall appeal of the project.


Project proposals should be clear and concise, but comprehensive. Different funding agencies use different formats of presentation and it is sensible to adopt these formats as early as possible. The process of preparation is sufficiently time consuming without additional unnecessary delays, especially where projects have a defined season of implementation.

Basic Questions

There are several basic questions that have to be asked when a project proposal is being developed. The list below is not necessarily exhaustive.

a. What are the genuine needs to be served ?
b. Can they and have they been identified ?
c. What objectives can the project actually achieve ?
d. Are the technologies appropriate and economically feasible?
e. What constraints, technical, social and economic are to be overcome ?
f. What are the long term implications ?

When these questions are answered it is important to present the basis of each answer and provide a summary of the research material. For example the answer to questions 'a' and 'b' may be based on extensive questionnaires; government economic or agricultural statistics; discussions with research organisations or workers already in the field. Questions 'c', 'd' and 'e' demand recourse to previous experience from other projects, noting advances made and failures due to identifiable causes. Sensible answers to question 'f' show that the long term development of a project has been well thought through. They indicate a familiarity with the host country and recipients and an understanding of what can and cannot reasonably be expected. Negative answers do not necessarily prove that a project is totally unsuitable, the long term implications may be simply too optimistic. Modification of the proposals may overcome any long term difficulties that come to light.

Background Information

The type of information needed will obviously be determined by the kind of project that is proposed. Consideration should be given the following:

a. National, regional and socio-economic information.

In general, bi-partite projects will have fewer problems in obtaining this information than ones involving various groups. However, such information is not always easy to get; it may even not be available, it may be seriously outdated and governments are sometimes reluctant to give it. Previous reviews and surveys provide a good indication of the width and availability of researchable material.

b. Previous, current and future projects.

These can often be a very valuable source of information, in addition to background research, technical data and research conclusions may be available. Learning from previous mistakes is an opportunity to be taken. Areas of cooperation can be explored, sometimes to the general benefit of all, but these areas should be clearly decided upon and defined.

c. Host government policies.

It is essential that projects be concordant to the policies of the host government. Any that are not are bound to fail and any long terms benefits will be lost. The opportunity to gain familiarity with organisations and individuals within government should be taken to the full.

Reporting and Evaluation

Reporting on project achievements should be undertaken in a systematic manner. Agreed arrangements should be made, which specify the details of reporting methods:

- From whom / to whom
- How often and at what length
- Whether technical or financial or both

Evaluations should include:

- Against what objectives any achievements should be assessed
- Details of the use of funds
- What dissemination of information has been undertaken
- Technical evaluations

Project Support

Project support can take many forms and should come from both inside and outside government. It may be through the cooperation with complementary projects which saves costs and provides a wider range of inputs. It may take the form of organised seminars and discussions which give a wider audience to the aims and achievements of project work. It may include the dissemination of information through government departments. The involvement of local institutions and experts is beneficial to both project and participants. Where a considerable financial burden may fall on participants (for example travel fares and housing of conference delegates), it is important that the responsibility for these costs to be identified and budgeted for.


One of the greatest benefits a project can leave behind is well trained staff There are however several conditions to this statement that must be given serious thought:

-The correct type of staff must selected and the level of suitable training must be clearly identified. This may be vocational or institutional. If the latter, the correct course must be sought and places obtained. A careful timetable is necessary.

- Host government obligations. Funding may be the responsibility of the project or government, or both. It may not be to the advantage of host governments to pay for training for local project staff who later return expecting an enhanced position and better career prospects. The details of such matters should be settled well before training is arranged.

- The training must be appropriate for re-deployment when the project is finished. Any training must be in the long term interests of the host government, especially where counterpart staff are concerned.

- Project obligations. It should be ascertained that the project budget provides funding for training, as some may not.

- International Centres. Some international centres will sponsor candidates for training, but early enquiries should be made, because such sponsorship is eagerly sought.

Practical Problems

The collection of good quality field data is frequently very difficult and many problems will be peculiar to individual projects. However, the two most general but almost universal problems that must be faced by research and field staff are:

- Collecting adequate information during the limited lifetime of a project
- Balancing resources between the amount and quality of data that can be collected.

These are problems that face almost every project as a whole and a cooperative effort is needed from all staff to overcome them, but below is a discussion of common difficulties that will probably be encountered by individual field workers in the attempt to obtain good data.

Limited Project resources: Projects in developing countries often succumb to the temptation of over-stretching their resources. In areas where little data is available and there is much to collect, the relative merits of few sites with intensive data collection and many sites collecting fewer data, must be carefully weighed.

Difficult access to sites: This is especially true of wet seasons when bad roads often become impassable. In such situations sites cannot be visited, equipment repaired, conditions observed nor site staff consulted. Sites should be carefully selected so as not to impose an intolerable burden on the data-collection routine.

Restrictions on transport to cover sufficient sites: The availability of transport and the means by which it is kept in good repair often pose some of the most serious logistic/resource problems that projects face in developing countries. Roads are usually bad, vehicle maintenance standards low and shortages of spare parts common. There is an understandable temptation for vehicles to be put to non-project uses in countries with rudimentary public transport facilities. This situation is not helped by the status which is conferred upon drivers, where the private ownership of vehicles is a great luxury.

Hostile physical environment: Equipment has a hard life. Rough and inexperienced handling, transportation in difficult conditions often leads to early breakdown. High humidity and large ranges of both seasonal and diurnal temperatures frequently take their toll. Given the difficulties of repair and replacement, equipment should be treated carefully and be well maintained. An adequate provision of spare parts should be made.

Inappropriate equipment: Very often equipment must be ordered from overseas. It is essential that the correct equipment be selected in the first instance. Replacement may be impossible or may take many months.

Inexperienced staff: It must be recognised that educational and training levels in developing countries are commonly lower than those in developed countries. This puts a great responsibility on professional project members to give as wide a range of relevant training as possible to technicians and field staff. Ideally, initial planning should place training as a core component of project activities, but this is by no means always so and in some instances research budgets actually preclude the use of project funds for training purposes. Initial project proposals should seriously consider the role of training in the future of any project. There is little more dispiriting to all concerned than a project which leaves no continuing activity behind at the end of its life.

Under-motivated staff: It may seem to project professionals working abroad, that local staff do not always give what they can toward the success of a project. When this is true, it is usually for very good reasons. Local staff almost always have very poor pay and conditions compared to expatriates. Often they are seconded from other areas of activity, sometimes on a temporary basis, with little hope of an enhanced career or improved personal prospects. They are often not trained nor aware of the opportunities that a project may offer. In developing countries, as in developed countries, technical personnel are undervalued in general; an administrative post in a ministry is far more likely to lead to promotion than supervising a field team. It is essential that local technical and field staff are shown that the success of any project lies very much in their hands. Without reliable, accurate information collected at the correct time, projects in the area of agrohydrology are little more than an exercise in redistributing a given amount of money.

These difficulties can never be totally overcome, but the careful selection, siting, installation and maintenance of equipment allied with good staff training can keep damage and disappointment to a minimum.