Water and energy efficiency in pressurised irrigation: efficiency, uniformity testing, maintenance and support

Pressurised systems carry water in pipes and deliver it close to the plant, so conveyance and distribution losses are lower than with open canals and flood irrigation. According to the 2025 activity report of DSİ, Türkiye's State Hydraulic Works, conventional systems deliver on average 3.75 l/s per hectare, while sprinkler and drip deliver 1.25 l/s; switching to closed pressurised pipe systems can save 35% of water under sprinklers and 65% under drip (DSİ, 2026).

Application efficiency: how much water does each method lose?

Application efficiency (Ea) is the share of the water applied that is stored in the root zone. The Crop Water Consumption Guide of TAGEM and DSİ uses the following values in project calculations (TAGEM and DSİ, 2017):

In piped networks conveyance efficiency is taken as 98%, and the gross requirement is the net requirement divided by the product of the two efficiencies. For a net requirement of 50 mm, surface drip needs about 57 mm of water and a portable sprinkler about 73 mm. The 16 mm difference equals 160 m³ per hectare, and every cubic metre pumped shows up on the energy bill. In design, when manufacturer data are lacking, the pressure difference within a sub-unit is limited to about 10% of the emitter operating pressure, which keeps the flow difference between emitters small (Savva and Frenken, 2002).

Drip, micro-sprinklers, subsurface drip and fertigation

The FAO irrigation manual lists the advantages of localised systems as follows: evaporation falls because only part of the soil is wetted (more so with young trees), fewer weeds grow, and deep percolation and runoff losses drop substantially. The drawbacks are also clear: emitter openings are small, so they clog easily and need good filtration; salts build up at the edges of the wetted zone, and a light rain can wash them into the root zone, so running the system during light rain is recommended (Savva and Frenken, 2002). Micro-sprinklers wet a wider area under the tree; subsurface drip buries the laterals and reaches the highest efficiency in the guide.

In fertigation the fertiliser travels with the water, so uniformity becomes even more important (USDA NRCS, 2015). FAO recommends connecting the injection unit between the pump and the filters, and finishing fertigation 20-30 minutes before the system is switched off, so that all nutrients leave the pipes before irrigation ends (Savva and Frenken, 2002).

How to run a uniformity test

In drip and micro systems, emission uniformity (EU) is measured with the low-quarter method. The procedure in the Florida field handbook of the US Department of Agriculture Natural Resources Conservation Service (USDA NRCS) is:

1. Start the system and wait 5-10 minutes for the pressure to stabilise.
2. Choose 16 emitters on 4 laterals of a representative manifold.
3. Collect the water of each emitter in a graduated cylinder: 60 seconds for drippers, 30 seconds for micro-sprinklers.
4. Measure the pressure at the inlet and the end of the laterals.
5. Calculate the average of all 16 readings and the average of the lowest 4: EU = low-quarter average / overall average × 100.

According to the handbook, above 90% is excellent, 80-90% good, 70-80% fair and below 70% poor. For example, if the 16 emitters average 3.8 l/h and the lowest four average 3.2 l/h, EU = 3.2 / 3.8 × 100 ≈ 84%, which is “good” (hypothetical figures). Low EU usually comes from clogging at the ends of laterals, pressure differences between manifolds, or mixed emitters with different flow rates (USDA NRCS, 2015).

Filtration and maintenance

• Filter pressure difference: Record inlet and outlet pressure at the filters every day. Clean a screen filter when the pressure difference has risen by 35 kPa; the maximum recommended pressure drop across sand filters is 70 kPa. Backwashing requires at least two sand filters, followed by a screen or disc filter.
• Lime precipitation: With bicarbonate at 2 meq/l or more and pH above 7.5, calcium precipitation is likely; acid (usually hydrochloric or sulphuric) is injected to bring pH to 5.5-7, with the dose set by laboratory titration.
• Iron and bacterial slime: Iron can cause clogging even at levels as low as 0.3 ppm. In chlorination the target is 1 ppm free chlorine at the end of the lateral.
• Flushing: Open the ends of manifolds and laterals periodically, one at a time; flush more often in warm weather.
• Water meter: A meter installed after the filters immediately shows flow above design (broken pipe or open lateral end) or below design (clogging or loaded filters) (Savva and Frenken, 2002).

Support in Türkiye

Communiqué No. 2026/10 of the Ministry of Agriculture and Forestry, published in the Official Gazette on 3 April 2026, provides grants for water-saving irrigation systems in all 81 provinces. The grant covers 50% to 70% of the eligible project amount including VAT (Resmî Gazete, 2026):

• In-field drip and sprinkler: 50%
• Micro-sprinkler; centre pivot, linear and hose-reel systems; solar-powered irrigation: 60%
• Subsurface drip; smart irrigation and automation (sensors, control, remote management): 70%
• All items in basins where groundwater is insufficient and a water restriction has been declared: 70%

The eligible project amount cannot exceed 10 million TL. The project is prepared by an authorised agricultural engineer, and a water use permit or groundwater use certificate is required depending on the source. Applicants must be registered in the Ministry's registration systems and remain so for five years after payment, and the system must be installed in the field within 75 days of the grant contract. On the public side, DSİ's target under the 2025 Presidential Annual Programme was to convert 20 thousand hectares of open canal networks to closed pipe systems and to install electronic metering at 90 schemes (DSİ, 2026).

Measures under the Common Agricultural Policy in Greece

Intervention Π3-73-2.2 of Greece's CAP Strategic Plan 2023-2027 supports farm investments that contribute to water savings. Under the joint ministerial decision of 6 August 2026 (Government Gazette ΦΕΚ 4988 Β΄), the support rate is 70% of eligible expenditure. Eligible items include drip and fixed micro-sprinkler systems with a small wetting diameter, conversion of surface drip to subsurface drip, water meters, and integrated precision irrigation solutions with software, weather data networks, soil analysis, sensors, and automated and remote control. Large-coverage fixed sprinklers, self-propelled sprinkler guns and booms, furrow and basin irrigation are not supported. A water meter is mandatory for every irrigation investment. Upgrading an existing system requires an ex ante potential water saving of at least 20%, and where the water body is in less than good status for quantity reasons, an additional effective reduction in use of at least 10%. The investment must be consistent with the river basin management plans revised in 2024 and amount to at least EUR 5,000 (ΥΠΑΑΤ, 2026).

The context of the EU Water Framework Directive

Behind these conditions lies the EU Water Framework Directive (2000/60/EC). It requires a balance between groundwater abstraction and recharge and the achievement of good status in water bodies, and its programmes of measures include registers and prior authorisation for surface water and groundwater abstraction. Article 9 requires water pricing to give incentives for efficient use and an adequate contribution from agriculture to the recovery of the costs of water services; river basin management plans are updated every six years (EU, 2000). In the Pinios basin of Thessaly, irrigation accounts for 90-95% of total water use, and under the first river basin management plan most water bodies were classified as less than good. As the irrigated area grew from 105,000 hectares in 1977 to 242,447 hectares in 1994, groundwater levels in the central basin fell from 2-5 m to 10-15 m or more below the surface (JRC, 2020). The 10% effective reduction condition in the Greek decision is tied directly to the Directive's good status objective.

Sources

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2. FAO SAFR, 2002. Savva, A. P., Frenken, K.: Irrigation Manual, Volume IV, Module 9: Localized irrigation: planning, design, operation and maintenance (accessed 29 September 2026)
3. USDA NRCS Florida, 2015. Mobile Irrigation Lab Handbook, Chapter 4: Irrigation System Evaluations (arşiv sürümü) (accessed 29 September 2026)
4. DSİ Genel Müdürlüğü, 2026. 2025 Yılı İdare Faaliyet Raporu (accessed 29 September 2026)
5. Resmî Gazete, 2026. Kırsal Kalkınma Yatırım Programı Kapsamında Tasarruflu Tarımsal Sulama Sistemlerine Yönelik Yatırımların Desteklenmesi Hakkında Tebliğ (Tebliğ No: 2026/10), Sayı 33213, 3 Nisan 2026 (accessed 29 September 2026)
6. ΥΠΑΑΤ και ΑΑΔΕ, 2026. ΚΥΑ 207871/06-08-2026 (ΦΕΚ 4988 Β΄): Καθορισμός πλαισίου εφαρμογής των Παρεμβάσεων Π3-73-2.1, Π3-73-2.2 και Π3-73-2.6 του ΣΣ ΚΑΠ 2023-2027 (accessed 29 September 2026)
7. Avrupa Birliği, 2000. Directive 2000/60/EC establishing a framework for Community action in the field of water policy (Water Framework Directive), Official Journal L 327 (accessed 29 September 2026)
8. European Commission Joint Research Centre (JRC), 2020. Fact sheet: Pinios River Basin (accessed 29 September 2026)