Improved Water Mill

In 1984 German Appropriate Technology Exchange of the German Technical Cooperation (GATE/GTZ) initiated IWM dissemination program. Various attempts were made, in the past, by the institutions and individuals both inside and outside the country for the improvement of traditional watermill. From 1990 onwards, Center for Rural Technology, Nepal (CRT/N), with the assistance of GTZ and other development organizations has been actively involved in the promotion and dissemination of IWM by motivating and supporting traditional mill owners.CRT/N with the assistance from Netherlands Development Organization (SNV/N) and Alternative Energy Promotion Center is implementing a five-year IWM support programme since 2003.
Traditional Watermill
Low power output watermill (pani ghatta) has been used in Nepal for centuries  as a source of energy for food processing services, in the form of cereal grinding, paddy hulling, oil extraction etc. These mills, with wooden blade, are run by the hydropower. In the mid hills of the country these mills are located at the banlk of streams and rivers.  Approximately more than 25, 000 traditional mills are in operation throughout the country. Watermills have been the part of of villages for centuries however, due to its low efficiency, it has not been able to meet the increasing procssing needs and other energy requirements of the rural communities.
Diesel engines are rapidly increasing  in high agro processing demand areas.  These diesel engines not only polluted the environment but also increased the dependancy on imported machinery and diesel. Freely available natural resources, whose utility can be highly enhanced by introducing a better and morfe efficient technology, are being waisted because of diesel engine.
Improved Water Mill
Improved water mills is an intermediate and reliable technology, with increased output (upto 3kW), based on the principle of traditional mills.
Advantsges of IWM:

  • can be used longer period in the dry season.
  • can offer diversified range of services(hulling, oil expelling, saw milling)
  • improved service quality-thus higher agro procesing capacity (milling capacity often doubles)
  • increased outpout thus service quality of the milling can be improved.
  • creates opportunity to genearte electricity for rural lighting, however this depends upon the flow and ahead avaialable.

This technology has been proven, through the extensive test over the last two decades, as appropriate and compatible with the rural environment.  This technology (IWM) has also helped in inducing positive changes in the socio economic conditions of the local millers and the whole community.

IWM is undoubtedly one of the most efficient options for assisting the rural communities in improving their quality of livelihood through various ways:
by saving the time spent on grinding
reduces the workload to the women
employment generation through local agro processing



Technical Features of IWM

Various components have been improved in the improved water mill however the most significantly the wooden runner, of traditional mill, was replced with hydraulically better shaped mettalic runner having cup shaped blades. This has increased its operational efficiency as well as making it more useful with additional machines for hulling, electricity generation etc.

The basic technical features of the traditional and improved water mill are as belows:

Parts of Traditional Water Mill

Parts of Improved Water Mill

Wooden water wheel with flat paddles

Metal runners with buckets

Wooden hub covers the metal vertical shaft

Metal vertical shaft

Wooden open chute of uniform cross-section

HDPE pipes


A pulley and belt system is introduced to belt-drive rice huller and electric generator


  • the power output ranges from 0.5kW to 3kW
  • the grinding capacity ranges from 20-50 kg maize per hour.
  • its repair/maintenance is low
  • life span is around 10 years. The chute which was mostly wooden has now been replaced by High Density Polyethylene (HDPE) pipes.

The basic functional features of the traditional and improved water mill are as belows:

Comparison Parameter

Traditional Water

Improved Water

Functional range



Length of canal



Length of canal

3-7 (max)


Water Discharge, lps



Speed, rpm



Inclination to chute, degree



Output power capacity, kW



Grinding stone



Operational efficiency, %

Below 25


Functions and capacity

Grinding cereal grains only (maize, wheat, millet rice etc), 10-20kg/hr

Grinding of cereals (20-20kg/hr)Maize: 35, wheat: 40, millet: 70



Dehusking/partial polishing of paddy (50-70 kg/hr)



Expelling oil from oil seeds (10-15 kg/hr)