Dieter Prinz and A.H.MalikInstitute of Water Resources Management,Hydraulicand Rural Engineering,Dept.of Rural Engineering,University of Karlsruhe,D-76128 Karlsruhe,Germany1 IntroductionDue to an ever increasing world population,improving standard of living,irregularities caused by global climate change and growing water pollution,the world water problems aggravating day by day.Especially the drier parts of the tropics and subtropics,but also countries in temperate climates,experience severe water supply problems-and agriculture will be hit hard-est.Agriculture utilizes globally about 70%of all the water managed by man,and about 80% of the water used in the developing world（Prinz 2000）.At the same time,the competition be-tween the various sectors-agriculture,communities,industry,nature,becomes stiffer and agriculture will be the loser in the run for scarce water resources,as the output per unit water is of significantly lower value than in the other economic sectors.On the other hand,the need for more food asks also for more irrigation water,therefore we have to find ways of growing more food with less water（Agarwal 2001）.But it is not only a problem of water quantity,but of quality due to increasing pollution,too.2 General overviewWhat is Water Conservation in general?Water conservation is the physical control,protection,management,and use of water resources in such a way as to maintain crop,grazing,and forest lands,vegetative cover,wildlife,and wildlife habitat for maximum sustained benefits for people,agriculture,industry,commerce,and other segments of the national economy.Water conservation in agriculture may be defined as the application of measures designed,to improve the availability of water for agricultural purposes（“Supply Management”）,to re-duce the present size of water demand（“Demand Management”）,and,to keep water re-sources from being polluted or wasted（Prinz ＆ Malik 2001）.The solutions found must be sustainable and possible negative effects e.g.on nature have to be avoided.Water conservation must be an integral part of“Integrated Water Resources Management”，a long-term integrated strategy which seeks to make best use of the available water resources（Fig.1）.Major features are:Surface water management:By diverting（more）water from rivers,e.g.by construction of hydraulic structures in rivers considerable quantities of water can be saved and used for agriculture,especially during the rainy season and under flood conditions.More reservoirs of high water holding efficiency are needed in future to cope with future water demands.Groundwater management:Groundwater tables are falling in most parts of the world and sustainable groundwater management deserves artificial groundwater recharge.Surface-and groundwater have to be used in a conjunctive way.Fig.1 “Integrated Water Resources Management”systemThe multiple use of water（“using every drop of water four times before draining it”）is essential to cope with future water demand.Rainwater management:Rainwater management can be either“in-situ moisture conservation”or“Water Harvesting”.Water Harvesting is defined as“the collection and concentration of rainfall（and overland flow）and its use for the irrigation of crops,pastures and trees for domestic and livestock consumption”.The water storage can be done in the soil matrix or in a reservoir（Oweis et al.,2001）.Rain and surface runoff management serves also the purposes of soil conservation,-a prerequisite for water conservation-,and flood control.The use of waste water,drainage water and other marginal water sources becomes more and more imperative to cover the demand.It is one of those measures which need very close supervision to avoid damage to soils and plants-at least on a long term.Wherever the natural conditions allow it,the use of fog and dew should be promoted to cover agricultural water demand.Besides these supply side measures we have a wide variety of water demand management measures,which can be grouped into:（1）Measures to reduce losses,and（2）Measures to increase the efficiency of water applied.As these demand side measures are regarded as the core measures of water conservation,water conservation is often defined as“measures designed to promote efficient use of water and to eliminate waste of water”.3 Socio.economic FactorsImportant socio-economic factors（Fig.2）of water conservation are:Fig.2 Main factors on the success of a water conservation project（1）Population stabilization reduces also pressure on water resources.（2）Community involvement is essential for effective water conservation.（3）Access to water can be viewed as a human right,therefore a fair distribution should be aimed for.（4）Water conservation should benefit from a multidisciplinary team.（5）Preference should be given to the application of nonstructural solutions,for example pricing of water.（6）To develop water conservation institutions,public education and awareness are essential.（7）Selection of appropriate low cost technology is a prerequisite for widespread implementation.（8）Planners should consider both traditional and modern technologies.（9）The price of water determines largely the investments justified to avaid water losses.Criteria to select water conservation measures are according to Emerson（1998）：（1）program costs， （8）cost-effectiveness,（2）ease of implementation， （9）budgetary considerations，（3）staff resources and capability, （10）environmental impacts，（4）rate payer impacts， （11）environmental and social justice，（5）water rights and permits， （12）legal issues or constraints，（6）regulatory approvals, （13）public acceptance，（7）timeliness of savings,and （14）consistency with other programs.Lessons learnt from various projects are that the adoption of a new irrigation system depends on farmer"s capacity to finance and operate it,as well as on the type of crop being produced.A modernised surface irrigation might be a better water saving technique than drip or sprinkler irrigation in certain locations;the latter ones are often not affordable.A modernised“old”system is also more easily adopted by farmers since it is closer to traditional practices.To achieve optimum water conservation＆improved water use efficiency,a water conservation enabling environment is needed that includes（Fig.3,4）：①education and training,improvement of systems and public incentives:these measures might allow in increase in further 20%～30%；②irrigation management transfer to users,management of supply infrastructure and an optimised resource policy to arrive at 60% to 80% of the potential；③further research of the public and the private sector to utilise fully the whole available potential.Fig.3 Ways of making better use of production potential in industrialized countries Source:Wolff＆Stein 1998（redrawn）,based on Cape 1995（Original data based on Australian conditions）Fig.4 Ways of making better use of production potential in developing countriesReferences[1]Agarwal A.Increasing water harvesting and water conservation is the only way to ensure food security.Down to.Earth,Vol 10,No.3,June 30,2001.[2]Cape J.Irrigation Research:Past,present and future.Irrigation Australia,1995,Vol.10,30～32.[3]Chritchley W.,Reij C.and Turner S.D.Soil and water conservation in Sub-Saharan Africa:to-wards sustainable production by the rural poor.IFAD,Rome and CDCS,Amsterdam.1992.[4]Emerson H.Conservation,it"s the future of water.On Tap,1998,Vol.7,Isse 4.[5]Oweis T.,Prinz D.and Hachum A.Water harvesting,indigenous knowledge for the future of the drier environments,ICARDA,Aleppo,Syria,2001,36pp.[6]Prinz D.Global and European water challenges in the 21st century.Keynote Speech,3rd Inter-Regional Conference on Environment-Water，“Water Resources Management in the 21st Century”，1-3 June 2000,Budapest/Hungary.Proceedings,2000,p.247～254.[7]Prinz D.and Malik A.H.Water Conservation in Agriculture,FAO Training Course,Draft Version on CD ROM,FAO,Rom.2001.[8]Wolff P.and Stein T.M:Water efficiency and conservation in agriculture-opportunities and limitations. Agriculture+Rural Development,1998,vol 5;no 2;pp 17～20.
