ERT 468 SURFACE WATER MANAGEMENT Prepared By: Mdm. Fathin Ayuni Azizan Lecturer, Biosystems Engineering Programme LECTURE WEEK 5: IRRIGATION FACILITIES & IRRIGATION CONVEYANCE

Course Content Water intake facilities: irrigation diversion intake system (surface & GW intake). Farm water delivery & storage system: various form of open channel or pipelines Pond & tank water storage

1.0 introduction Irrigation water (surface/GW) delivered -> farm by; gravity pumping It requires: diversions & intakes intake structure built at the entry to IS Divert water from sources (pond/river/reservoir/aquifer) into the IS.

2.0: TYPES OF INTAKE STUCTURE 2.1: River Intake (RI) Designed so that the required Q can be diverted or pumped at all times (even during extreme low flow) Design considerations include: topography soil conditions hydrology & hydraulics design discharge water availability low flow conditions

Divert water directly from a river thro diversion structure (a) Gravity-fed RI Divert water directly from a river thro diversion structure diversion structure task: Diverting & regulating the quantity of river water to primary canal (a) Gated Control Gravity Intake Primary Canal

(b) Pumped RI Pump is used when river water level below the level of the irrigated fields Several types of pumps can be used but the most common is ‘centrifugal pump’ Pump house Vertical Centrifugal Pump Pumping plants required when water must be lifted from the water source Pump type Horizontal centrifugal pumps -> used for surface water sources, pump is above the water surface. Vertical centrifugal pumps -> used with either surface or GW sources

Vertical Pumping plants

Intake Site Selection for River Intake: Site free from change of river flow direction, rise/fall in the river bed level with calm & gentle flow Site of good geological formation & safe from landslides/scouring. Water quality safe from pollution & intrusion of sea water Site shall be of easy access & spacious for future extensions & maintenance works

2.2 Impoundment Intake (II) Involves construction of dam & storage reservoir Water supplied by gravity & better quality than river water Types of dam: concrete/masonry dam earthen dam

Intake Site Selection for Impoundment Intake: Site closed to the irrigation canal as possible Site with good road access so that construction & maintenance works can be done Site having asses to natural drainage to drain excess reservoir water

2.3 Groundwater Intake (GWI) Water abstracted by shallow/deep wells Advantages: Can be abstract any time of the day/year. better water quality. Do not require storage reservoirs & long delivery pipes GW pumping system

Intake Site Selection for Groundwater Intake: Site must have good aquifer condition It located centre or close to the irrigation project. location of the tube-wells not within the radius of influence of other wells Site can provide good water quality

3.0: STRUCTURES OF SURFACE WATER INTAKE a) Canal Head Works 2 structures are necessary to construct: Structure across the river Structure at the head of canal called “barrage” called “Head Regulator”

(b) Reservoir Outlet Works (c) Pumping Station

4.0: STRUCTURES OF GROUNDWATER INTAKE a) Water Wells a hole, usually vertical, excavated in the earth for withdrawal of GW.

(b) Tube-well Components

5.0: IRRIGATION CONVEYANCE Carry water: source farms In the form of: open channels Pipelines Capacity sufficient to meet: any amount any where any time Designed as: environmental friendly easy to operate & maintain economically justified Or combination of both

IRRIGATION CANAL PRIMARY CANAL SECONDARY CANAL TERTIARY CANAL

- sloped to the direction of flow - either lined or unlined (i) Lined: (a) Open Channels - sloped to the direction of flow - either lined or unlined (i) Lined: lined with hard surfaces (concrete & asphalt) covered with membranes or soil sealants to reduce maintenance costs, channel sizes & seepage losses (thro channel bed & walls) (ii) Unlined: used b’cos low capital costs & ease of construction & relocation

-laid on the ground surface or buried -classified as: (b) Pipelines -laid on the ground surface or buried -classified as: open (low head) closed (pressurized) (i) Low head pipelines : deliver water at pressure that only surface irrigation methods can be employed Pump is required if pressurized IS to be use (ii) Pressurized pipelines: deliver water under adequate pressure for the pressurized IS equipped with necessary accessories such as: flow regulator pressure regulator water meter air release & vacuum relief valves

6.0: selection of conveyance taking into consideration advantages & disadvantages (a) Open channel construction cost < pipeline employed when land is flat & flows are large (b) Pipeline Used when conveyance canal is too long due to topographic conditions & possible lower construction cost widely adopted in large-scale irrigation schemes buried in the ground Easier operation & Min. maintenance requirement Efficiency in water use & more amendable social condition to farmers

6.0: PLANNING & DESIGN CONSIDERATIONS Factors taken into consideration; Conveyance capacity Function of regulation, distribution & delivery Operation, maintenance & management of the system Safety of the canal system Harmony with environment What to design? Canal Layout Lined Canal Unlined Canal Pipelines

Design of Canal Layout

Systems Design

MUDA catchment area =965 km PEDU catchment area =171 km Ahning Dam PeduDam Muda Dam MUDA catchment area =965 km 2 PEDU catchment area =171 km KEDAH THAILAND GENERAL LAYOUT PLAN OF TERTIARY SYSTEM FOR BLOCK ACLBD 8b

a) Open Channel Design Design of Lined Canal Wetted perimeter, p Area of Cross-section, a Hydraulic radius, R P = b+c+c A =((b+t)/2) x d R = a/p

(b) Canal Discharge Capacity Common method for the design of lined/non-erodible channels are: Manning Formula Chezy’s Equation Discharge, Q (Manning formula), Where, Q = Discharge in canal (m3/s) n = Manning roughness coeff A = Cross-sect. area of water (m2) R = Hyd. radius (m) S = Slope of canal bed Where, Q= VA V = Q/A = 1/n (R2/3 S1/2)

Table of Values of Manning’s n Type and description of channels Manning’s n Earth Channels Straight and uniform Winding, Sluggish Slurry Bed, weeds on bank Small drainage ditches 0.023 0.025 0.035 0.040 Lined Channels Concrete Masonry, rubble Metal, smooth Wooden Vegetated waterways 0.015 0.017 – 0.030 0.011 – 0.015 0.011 – 0.014 0.020 – 0.040 Pipes Cast iron Concrete drain tile Steel Sewer pipes 0.012 – 0.013 0.011 0.015 – 0.017 0.013 – 0.015

Canal Types

Example: Assume an earth channel on a grade of 0.10 per cent, depth of water 40 cm, bottom width 40 cm and side slopes 1 ½ to 1. Calculate the velocity of flow water carrying capacity of the channel.

(c) Design Steps Step 1: Estimate Manning’s or Chezy’s coeff. Step 2: Use Figure 9.4 to determine flow depth (y). Step 3: Check if ‘y’ is within required limits for the canal type. If not, adjust the canal dimensions & return to step 2. Step 4: Calculate the ave. flow velocity from V = Q/A & check that it is within the max. & min. velocity criteria for the canal type. If not, adjust the canal dimensions & return to step 2. Step 5: Add required freeboard to ‘y’ & calculate top width of canal Step 6: If required, calculate width of canal reserve.

Design of Unlined Canal (a) General Design Concept Unlined canals properly designed to provide; Velocity such no serious scouring/sedimentation Sufficient to carry the design flow Hydraulic grade sufficient at a proper depth for good water management Sides slopes that are stables Low seepage loss Min. initial & maintenance costs.

(b) General Requirements (i) Losses Include seepage losses, evaporation losses & operational losses expressed in m3/d/m2 of wetted areas or mm/d. Seepage = 30 mm/day for lined canal to 20X or more for unlined canal. The loss of flow in each reach is computed as follows:   Qs = qs PL/84600 Where, Qs = flow loss to seepage in canal reach (m3/s) P = wetted parameter (m) L = length of canal reach (km) qs = rate of infiltration (mm/day =1/m2/day).

(ii) Freeboard To allow for an increase in the WL above the full supply level

(iii) Bank For operation, maintenance & inspection min. bank width along the canals will be required

Discharge capacity in pipelines Design of Pipelines Discharge capacity in pipelines The discharge capacity through a pipeline can be determined by applying the Darcy’s equation. V= velocity of flow of water through the pipe, cm/sec H= Available head causing flow (difference in elevation between water level), cm d= Diameter of pipe, cm g= acceleration due to gravity, cm/sec2 l= length of pipe f = Darcy’s roughness coefficient

Values of coefficient ‘f’ in Darcy’s equation for pipe flow Velocity, cm/sec

Example: Determine the discharge capacity of an underground concrete channel line from the following data : Diameter of pipe 15 cm, length of pipe line 150 meters, difference in elevation between water levels at pump stand and discharge is two meters. Assume velocity to be 90cm/sec.

END of chapter 5/10/2017