Introduction Irrigation and drainage Systems LAB. SUMBERDAYA ALAM DAN LINGKUNGAN UB PUSAT STUDI LINGKUNGAN HIDUP UB BAMBANG RAHADI

Surface Irrigation Methods -- Discussion 3 1.BAHASAN-- 1.APA YANG DIMAKSUD IRIGASI PERMUKAAN? 2.METODE APA YANG DIGUNAKAN? 3.BERAPA LUAS? BERAPA JARAK DARI SALURAN UTAMA? 4.PERLUKAH MEMPERGUNAKAN AIRTANAH? 2. EFISIENSI 1. BAGAIMANA DENGAN KONDISI LAHAN DI INDONESIA? 2.BAGAIMANA CARA PENGUKURAN? 3. KESESUAIAN LAHAN– 1.BAGAIMANA LAYANAN YANG EFISIEN UNTUK PETANI.

IRIGASI PERMUKAAN WATER FLOWS ACROSS THE SOIL SURFACE TO THE POINT OF INFILTRATION OLDEST IRRIGATION METHOD AND MOST WIDELY USED WORLD-WIDE (90%) AND IN U.S. (60%) USED PRIMARILY ON AGRICULTURAL

Surface Irrigation Systems Water spreading Types of Surface Irrigation Systems  Basins  Borders  Furrows Water Supply and Management  Inlet Control  Land Leveling  Wastewater Recovery and Reuse Surface Irrigation Structures  Diversion Structures  Management Structures  Field Distribution Structures

Types of Surface Irrigation Systems – Water Spreading Water Spreading Water Spreading  Relatively flat fields -- allow water to find its own way across the surface  Minimal preparation and investment  Rather inefficient

Types of Surface Irrigation Systems -- Basins Basin Basin  Dikes used to surround an area and allow for water ponding (no runoff)  Basins are usually level

Types of Surface Irrigation Systems -- Borders Border Border  Strips of land with dikes on the sides  Usually graded but with no cross slope  Downstream end may be diked

Types of Surface Irrigation Systems -- Furrows Furrow Furrow  Small channels carry the water (entire surface is not wet)  Commonly used on row crops  Lateral as well as vertical infiltration  Furrows are usually graded

Land Leveling

Methods of water supply  siphon  Sekat balok

Reuse

Surface Irrigation Structures – Measurement Devices

Surface Irrigation Structures – Field Distribution Devices

Evaluation of Surface Irrigation Systems – Infiltration Evaluation of Surface Irrigation Systems – Infiltration

Evaluation of Surface Irrigation Systems – Flow Geometry Evaluation of Surface Irrigation Systems – Flow Geometry

Evaluation of Surface Irrigation Systems – Field Inflow Evaluation of Surface Irrigation Systems – Field Inflow

Evaluation of Surface Irrigation Systems – Field Outflow Evaluation of Surface Irrigation Systems – Field Outflow

Evaluation of Surface Irrigation Systems – Advance/Recession Evaluation of Surface Irrigation Systems – Advance/Recession

Surface Irrigation Hydraulics Advance Advance  Air bergerak dari masukan sampai keluaran di  Curve of Time vs. Distance is NOT linear  1/3 waktu pembasahan digunakan untuk mencapai tengah

Surface Irrigation Recession Recession  Proses air meninggalkan permukaan, setelan masukan dihentikan airanya.  Biasanya dimulai dari hulu pintu masukan.  plotted as Time vs. Distance  Lebih datar dibandingkan curva pembasahan.

Surface Irrigation Hydraulics Infiltration Infiltration  Opportunity Time: difference between Recession and Advance curves  Infiltration Depth: a function of the opportunity time and the infiltration class (rate) of the soil

Curve of Time Vs. Distance Distance from inlet end (ft)

Opportunity Time

Infiltration vs. Opportunity Time

Infiltration Profile

Uniformity Ketersediaan tidak seragam karena kurca recession dan advance tidak paralel. Ketersediaan tidak seragam karena kurca recession dan advance tidak paralel. Factors affecting Factors affecting  Laju pemasukan air  Slope  Infiltrasi  Kekasaran (koefisien manning)  Bentuk alur  Waktu pemasukan  Panjang alur

Efficiency Volume balance Volume balance  V g = V z + V s + V r  g  gross  z  infiltration  s  surface storage  r  runoff (or depth basis): d g = d z + d s + d r (or depth basis): d g = d z + d s + d r Part of infiltration may go to deep percolation Part of infiltration may go to deep percolation

Single furrow: Single furrow: Furrow set: Furrow set: Basin/border: Basin/border:

Example Problem

Example Problem Contd…

Other Design and Management Considerations Maximum non-erosive stream size: Maximum non-erosive stream size:  q max = maximum non-erosive stream size (gpm)  S = field slope (%) Set time and cutoff ratio: Set time and cutoff ratio:  CR = cutoff ratio  t L = advance time to the end of the field  t co = set time  Low CR's: rapid advance, good uniformity, high runoff  High CR's: slow advance, poor uniformity, low runoff

Improving Irrigation Efficiency Alternate furrow irrigation Alternate furrow irrigation  Increases advance time, but reduces average infiltration depth (twice the width) Cutback irrigation Cutback irrigation  Use large inflow rate during advance, and then reduce the inflow to match the soil's steady-state infiltration rate  Intensive management is required

Improving Irrigation Efficiency Cont’d Land smoothing and laser grading Land smoothing and laser grading  Helps to improve uniformity Surge irrigation Surge irrigation  Alternate on-off periods for applying water  Achieve higher efficiencies and uniformities in some soils  Lends itself to semi-automation

Runoff recovery systems Runoff recovery systems  Drainage ditches for collecting and conveying runoff to the reservoir  Reservoir for storing the runoff water  Inlet facilities to the reservoir (including desilting basin)  Pump and power unit  Conveyance system for transporting water (to same or different field)

End of Presentation 3