CONTENTS Sprinkler irrigation systems

Transcription

1 CONTENTS Sprinkler irrigatin systems 1 Intrductin Types f sprinkler irrigatin Cmpnents used in sprinkler irrigatin Main line Hydrant Lateral Stand pipe Flw cntrllers Flexible flw cntrl Spring laded flw cntrl Dragline hses Sprinklers Design nrms fr sprinkler irrigatin Factrs influencing sprinkler peratin Nzzle Pressure Spray angle Sprinkler rtatin Christiansen Unifrmity Cefficient Wetted area verlap Grss applicatin rate Evapratin lsses Chice f sprinkler Layut plan Design f sprinkler irrigatin Design prcedures Design Required infrmatin Site plan Evaptranspiratin Readily available water Net irrigatin requirement Grss irrigatin requirement Cycle length Area cvered per sprinkler Chice f sprinkler Grss applicatin rate Nett applicatin rate Stand time Number f sets per day Wrking hurs per day Number f sets per cycle Grss applicatin per cycle Number f sprinklers perating simultaneusly System capacity Layut plan

2 6 Hydraulic calculatins Stand pipe Dragline hse Lateral Pipe cuplings Other pipe fittings Final plan Side rll system References All rights reserved Cpyright 2003 ARC-Institute fr Agricultural Engineering (ARC-ILI) ISBN

3 Sprinkler irrigatin systems Intrductin In the sprinkler methd f irrigatin, water is applied abve the grund surface as a spray smewhat resembling rainfall. The spray is develped by the flw f water under pressure thrugh small rifices r nzzles. The pressure is usually btained by pumping, althugh it may be by gravity if the water surce is high enugh abve the area t be irrigated. The irrigatin water is distributed t the field thrugh pipelines. Sprinkler irrigatin is adaptable t mst crps, sils and tpgraphical circumstances. Hwever fr an ecnmical system and even water distributin ver the ttal land surface, careful judgement f the design criteria is required. With careful selectin f nzzle sizes, riser heights, perating pressure and sprinkler spacing, water can be applied unifrmly at a rate lwer than the intake rate f the sil, thereby preventing runff and the resulting damage t land and crps. 2 Types f sprinkler irrigatin The varius types available are described and illustrated in Chapter 10: Irrigatin Systems. The sprinkler system includes the sprinkler, the stand pipe, the lateral pipe, the main line pipe and ften the pumping plant. Cst will vary as a result f: distance and difference in height between water surce and centre f field; type f pwer surce. i.e. diesel r electric; spacing f sprinklers; applicatin rate; cycle time; quantity f water; and type and quality f material. The sprinkler system may be classified as permanent, semi- permanent r prtable accrding t the makeup f the cmpnents and the way it is used. The mst widely used distributin systems are: Prtable lateral with sprinklers mved as a whle. Semi-slid set nly sprinklers are mved. Dragline nly sprinklers and hses are mved. Big gun with prtable supply pipe where gun and supply pipe are mved. Side-rll mved as a whle. Permanent slid set.

4 13.2 Irrigatin Design Manual 3 Cmpnents used in sprinkler irrigatin The figure belw illustrates varius cmpnents that can be incrprated int a sprinkler irrigatin system. 3.1 Main line Figure 13.1: Cmpnents f sprinkler irrigatin The main line is a pipe which delivers water frm the pump t the laterals. They are nrmally laid belw grund (i.e. permanent) r laid abve grund (i.e. prtable) and have the largest diameter f the pipes in the system. The table belw can be used as a guideline and is based n the cst f the pipes. Table 13.1: Pipe selectin guideline Pipe Size [ mm] 50 Pipe Type Plyethylene upvc > 150 Fibre Cement, Steel and Cncrete Deviatins frm this may ccur if yu take wrking pressure, transprt distances, installatin csts and tender price int accunt.

5 Sprinkler Irrigatin Hydrant 1. Hydrant value 2. Valve 3. Main line 4. Lateral Figure 13.2: Hydrant cmpnents A main line (supply line) is cupled t a lateral by means f a hydrant. A stpcck and pressure gauge are prvided n the hydrant s that water can be delivered t the lateral at the crrect pressure. Quick cuplings are prvided at the hydrant valves s the water can be turned ff frm the lateral, which can be discnnected and recnnected at a new lcatin withut stpping the pump. With permanent undergrund laterals, hydrmatic valves are lcated at each sprinkler psitin. The sprinkler pipe is usually cupled t the nearest hydrant, t avid unnecessarily lng cnnectin pipes between the hydrant and sprinkler pipe. It is essential t determine whether at any stage tw laterals are perating simultaneusly frm ne specific hydrant. If this is the case, a T-Piece instead f an elbw jint must be used. 3.3 Lateral The lateral is a pipe which delivers water frm the main line t the sprinkler. It can either be prtable r permanent, and is usually smaller in diameter if cmpared t the main line. Prtable laterals are either aluminium r light steel pipe with plain cupling r lever-type cupling respectively. It is advisable t use mre than ne type f quick-cupling types in a system. One methd f mving laterals is by hand, where the pipe is uncupled, mved a length at a time and recupled. Permanent laterals are either plyethylene r upvc pipe with draglines attached. Fr the sake f cnvenience, mst farmers prefer lateral lines f a single pipe size. Sme farmers prefer t use tw pipe sizes which can result in a reductin in initial csts. Laterals cntaining mre than tw pipe sizes are nt recmmended. Pressure-reducing valves are used in laterals where the tpgraphy is undulating r t steep t restrict pressure variatin in the line t within the 20% limit by the selectin f practical pipe sizes r by means f hydrant valves.

6 13.4 Irrigatin Design Manual 3.4 Stand pipe Stand pipes are smaller diameter pipes which cnnect the sprinkler t the lateral r dragline hse. In a prtable r semi-permanent system mainly galvanised steel stand pipes are used, while in a permanent system use is made f upvc r plyethylene stand pipes. Stand pipes must be prvided in rder t remve the turbulence when the directin f flw is changed by diverting a part f the flw t an individual sprinkler. If nt remved, this turbulence will carry thrugh the nzzle and cause a premature stream break-up and a reduced diameter f cverage and thereby a prer distributin pattern. The length f pipe needed t remve turbulence varies with sprinkler discharge. Table 13.2: Recmmended minimum stand pipe length Sprinkler Discharge [ m³ / h ] Stand Pipe Length [ mm ] up t The sprinkler shuld be placed at least 0,6 m abve the crp. Stand pipes are nrmally available in the fllwing lengths: 0,2 m; 0,5 m; 1,0 m; 1,2 m; 1,5 m; 2 m and 3 m (they can als be custmised) with diameters ranging frm 20 t 25 mm. 3.5 Flw cntrllers Due t the uneven distributin thrugh a sprinkler system caused by field elevatin differences, excessive pipe frictin lss and variatins in pump pressure, there is a need t cntrl the flw. The satisfactry perfrmance f impact-drive rtating sprinkler depends t a large extent n perating flw rate. There is n ne place alng the pipe where a single flw cntrl can be installed that will handle an entire system. Hwever, cntrl can be exercised by having a flw cntrl at each sprinkler head. Mre unifrm water applicatin can imprved crp yields, reduce pumping csts and save in water and chemicals. The bdies are made f brass r mulded plastic. Flw cntrl devices will nly reduce the flw, but it will nt increase a flw rate that is inadequate. Tw methds f flw cntrl are t fit either a flexible flw cntrl device r a spring-laded flw cntrl t the system Flexible flw cntrl There are tw types f flexible flw cntrllers: Flw cntrl nzzle Wrking - The flw cntrl nzzle is fitted in place f the standard impact sprinkler nzzle which helps t equalize the flw rate frm each sprinkler. - As the pressure increases s the flexible rifice cntracts allwing the discharge t be held cnstant regardless f pressure fluctuatins. - The available flw rate ranges frm 0,30 /s t 0,49 /s. - The wrking pressure range is 14 t 56 m, with recmmended perating pressure 17 t 35 m.

7 Sprinkler Irrigatin 13.5 Advantages - Designed fr lw pressure peratin. - The unique teardrp shaped rifice is designed t prduce the mst desirable distributin pattern and drplet size at lw pressure. - The single rifice design and self-flushing actin minimises plugging. - Maintain flw rate accuracy f plus r minus 10% f the perfrmance curves. - The stream diffusin imprves water distributin unifrmity f a sprinkler and reduces the drplet size at lw pressures. - Since the stream is discharged acrss the rifice directly int the atmsphere, the pressure drp nrmally assciated with flw cntrl devices des nt ccur. Disadvantages - If perated in high wind cnditins the wetting pattern is distrted mre easily than the standard nzzle patterns. - D nt use excessively wide sprinkler spacings, ptimise at 12 m by 15 m. The wider spacing will reduce unifrmity f applicatin. - The rifice can easily blck, which will change the distributin pattern f the sprinkler. - Due t the material f the device it is susceptible t wear. - The distributin pattern changes with an increase in pressure. Figure 13.3: Flw cntrl nzzle Flexible rifice Wrking - Simple and effective in design and use. - The rifice changes shape t maintain a cnstant flw rate as the inlet pressure increases. - Operates n the same principal as the flw cntrl nzzle. - The device is designed t deliver a cnstant vlume f water frm any utlet whether the pressure is 10 m r 85 m. - The cntrlling mechanism cnsists f a flexible rifice that varies it s area inversely with the pressure s that a cnstant flw rate is maintained. Advantages - The device is self-cleaning. - The device is nt prne t scaling. - Respnse t pressure variatin is instantaneus. - Flw rates are accurate within plus r minus 10% f the nrmal flw rate. - Cnsidering individual flw cntrls, the rate will stay within 5% t 8% f the mean flw rate thrugh the full range.

8 13.6 Irrigatin Design Manual Disadvantages - The rifice can easily blck, which will change the distributin pattern f the sprinkler. - Due t the material f the prduct it is susceptible t wear Spring laded flw cntrl Figure 13.4: Flexible rifice Wrking These flw cntrllers functin by means f a regulating spring which is enclsed in a sealed chamber. The utging pressure acts n a diaphragm which cmpresses the spring and causes a thrttling actin n the inlet flw. There are nine clur-cded reducers varying frm 4,3 m t 35 m. The flw rate which can be handled varies frm 0,3 m³/h t 4 m³/h. Advantages At a pressure belw the set regulatin pressure, the thrttling actin is negligible. Can perate at a maximum cntinuus pressure f 70 m but can withstand pressure surges f an extremely shrt duratin. By placing a reducer at the beginning f each lateral, enables the designer t set the same pressure at the beginning f each line in the system. The allwable pressure variatin can be restricted t the lateral alne and allw the use f lnger and thinner pipes. Disadvantages Due t the material used it is susceptible t wear. An expensive item in cmparisn t the flexible flw cntrllers.

9 Sprinkler Irrigatin 13.7 Figure 13.5: Spring laded flw cntrl 3.6 Dragline hses Figure 13.6: Dragline hse cnnectin Dragline hses are used where a sprinkler is cnnected t ne end and a lateral pipe t the ther end. The sprinklers can then be mved withut displacing the pipeline. The pipe diameters range between 15 mm and 25 mm (inside diameter) and the length f pipe nrmally varies between 18 m and 45 m and is made f UV treated plyester reinfrced PVC material. The mst cmmn size f pipe used is 20 mm. 3.7 Sprinklers Figure 13.7: Sprinkler cmpnents

10 13.8 Irrigatin Design Manual Many sprinklers n the market are sld tgether with technical dcumentatin. When chsing a sprinkler the fllwing must be taken int accunt: Unifrmity f water applicatin. Precipitatin rate: Functin f discharge, wetted diameter and sprinkler spacing. Drp size distributin: Functin f nzzle diameter, pressure and pressure variatin. The cst. Back-up service Fur general types f sprinklers are used: Rtating sprinklers agriculture Flppy sprinklers agriculture Fixed nzzles attached t the pipe hrticulture. Perfrated pipe nursery and gardens. The impact-drive rtating sprinkler is the mst ppular. The impact drive has a weighted springladed drive arm t prvide the frce t rtate the nzzle assembly. The sprinkling stream deflects the arm sideways and the spring pulls the arm back t the nzzle assembly and int the path f the stream. As the drive arm cmpletes each swing cycle it impacts against the nzzle assembly rtating it slightly. The advantage f the rtating sprinkler is its ability t apply water at a slwer rate while using relatively large nzzle penings. Sprinklers can be divided accrding t pressure required: Table 13.3: Sprinkler categries Sprinklers Pressure [m] Flw rate [m³/h] Typical applicatin Lw pressure < 20 < 0,7 rchards Medium pressure < 3 cash crps High pressure > 40 < 50 pastures and sugarcane High vlume > pastures and maize The cnstant rtatinal speed is very imprtant, as a variatin will mean a variatin in the applicatin unifrmity. Large rtating sprinklers, perating at high pressures, are cmmnly referred t as big guns. The term big gun is derived frm the large gun like nzzle and its ability t distribute large quantities f water ver a wide area. They are nrmally munted n risers, supprted n a tripd r framewrk. Water is supplied t the sprinkler thrugh a flexible hse. The terrain f the land t be irrigated shuld be reasnably smth. Due t the high pressures, strng winds can influence the effective water distributin. These are high capacity, high pressure sprinklers, perating at pressures ranging frm 40 t 80 m, with a delivery utput ranging up t 70 m³/h.

11 Sprinkler Irrigatin Design nrms fr sprinkler irrigatin These design nrms are imprtant t ensure an efficient and effective sprinkler irrigatin system. 4.1 Factrs influencing sprinkler peratin The fllwing factrs can influence the peratin f a sprinkler irrigatin system Nzzle A sprinkler can have ne r three nzzles. The main nzzle determines the reach, while the secndary nzzles determine the distributin unifrmity. The nzzle is ne f the least expensive cmpnents, yet are ften neglected. Nzzle wear des ccur with time, which results in an enlargement f the rifice. A 10% enlargement f the rifice will result in an increase f abut 20% in delivery rate and a 20% increase in pwer cnsumptin. The nzzle determines the flw, breaks up the water int drplets and disperses them in a specific pattern and size fr desired effect. Tw- nzzle sprinklers have higher flexibility fr adjustment Pressure The discharge f a sprinkler is a functin f the nzzle diameter and pressure. The ptimum pressure at which a sprinkler must perate can be calculated using the fllwing rule f thumb: Operating pressure f the sprinkler [m] = 6 t 7 times the nzzle diameter [mm] Example 13.1: What is the perating pressure range f a 5 mm nzzle diameter? Slutin: 5 mm 6 = 30 m 5 mm 7 = 35 m Thus a 5 mm nzzle shuld perate between 30 m and 35 m pressure. Nte: Only applicable t main nzzle sizes between 3 mm and 7 mm. Each type f sprinkler has certain pattern characteristics that change as nzzle size and perating pressure change. Each has an ptimum range f perating pressures fr each nzzle size. At the lwer side f the specified pressure range fr any nzzle, the water is brken up int larger drps. When pressure falls t lw, the water frm the nzzle falls in a circle a distance away frm the sprinkler, thus giving a pr distributin dughnut like pattern. On the high side f the pressure range, the water frm the nzzle breaks up int finer drps and settles arund the sprinkler. Under such cnditins the wetting pattern is easily distrted by wind mvement. Fr a given pressure, larger drps are frmed by a large nzzle size and fine spray by a small nzzle.

12 13.10 Irrigatin Design Manual Spray angle Figure 13.8: Effect f different pressures n distributin pattern. The sprinkler spray angle influences hw high the water is prjected int the air. The higher the water is prjected, the wider the reach f the sprinkler. Hwever, this subjects the spray t higher wind speeds and larger pattern distrtin than water is ejected clser t the grund surface. The best angle fr a sprinkler jet under ideal cnditins is 32 abve the hrizntal. Hwever under windy cnditins, a lwer angle must be used t reduce the affect f wind. Mst medium size sprinklers are abut 25 t 26 degrees, whereas larger sprinklers are between 23 t 24 degrees. The selectin f the spray angle depends n the crp t be irrigated and the prevailing winds Sprinkler rtatin A cnstant sprinkler rtatin speed will give a gd distributin. An average f 2 rtatins per minute r an ptimum speed between 2,1 t 2,5 m/s n the uter circumference is recmmended Christiansen Unifrmity Cefficient (CU) A statistical parameter giving a descriptin f hw evenly the irrigatin water is distributed in an irrigatin blck, based n measurements f the Net Applicatin (NA) n a grid ver the given area. There is a measurable index f the degree f unifrmity btainable fr any size sprinkler perating under given cnditins. This CU-value is affected by pressure nzzle size relatins, by sprinkler spacing and by wind cnditins. The fllwing equatin can be used t determine the CU-value.

13 Sprinkler Irrigatin / xi C U = N - x / x (13.1) where CU = Christiansen Unifrmity Cefficient [%] = i th measurement [mm] i X = average measurement [mm] N = number f measurements The fllwing nrms are used under windless cnditins fr different crps. Table 13.4: CU Cefficients f unifrmity (Keller, 1990) CU [%] Crps Vegetables Deep rted field crps Trees This cefficient is determined fr sprinklers under labratry cnditins. Different sprinklers can be cmpared because they are tested under similar cnditins i.e. n wind, fixed pressure and three test repetitins. These tests are carried ut by the ARC-Institute fr Agricultural Engineering at Silvertn t prvide designers and the users f sprinklers with this valuable infrmatin which will enable them t cmpare sprinklers at different wrking pressures and spacings. It must be stressed that labratry CU-values are nt the same as field CU s but they prvide a basis fr cmparisn. 4.2 Wetted area verlap The required discharge f an individual sprinkler is a functin f the water applicatin rate and the tw-way spacing f the sprinklers. Unifrm distributin is achieved by verlapping n the lateral and between laterals. The verlapping depends n the required applicatin rate [mm/h], the discharge f the sprinkler [m 3 /h] and the general windspeed [km/h]. There are three types f sprinkler spacings: square, rectangular and triangular. Each type has certain advantages, but under average cnditins best results in terms f distributin unifrmity are usually btained frm a square spacing. The number f laterals n field can be reduced t lwer the system cst withut sacrificing by using a rectangular spacing. The distance between the laterals is increased and the distance between the sprinkler is decreased. Sme designers use the triangular spacing, but it des nt always lead t better results, especially when the sprinklers are relatively widely spaced.

14 13.12 Irrigatin Design Manual Figure 13.9: Types f sprinkler spacings A rule f thumb is that the maximum distance between sprinklers fr nrmal windspeed, is 60% f the wetted diameter f an individual sprinkler. T cmpensate fr wind, the fllwing adjustments can be made. Table 13.5: Wetted area verlap Windspeed [km/h] N wind Sprinkler spacing perpendicular t wind directin 65% f wetted diameter 0 6,5 55% f wetted diameter 6, % f wetted diameter > 13 30% f wetted diameter Cmmn practice is t assume a sprinkler spacing and determine the sprinkler discharge frm a table similar t Table Next, nzzle size, ptimum perating pressure, and diameter f the wetted area are btained frm the manufacturer's sprinkler perfrmance tables. The assumed spacing is then cmpared with the wetted diameter t assure that the required spacing criteria has been met. If this is nt the case, then different spacing may be assumed r a different nzzle size perating pressure cmbinatin selected. The fllwing example shws the wrking f Table Example 13.2: Assume the fllwing: Wind speed = 5 km/h Wetted Diameter = 26,8 m Sprinkler Spacing = 12 m Lateral Spacing = 12 m Slutin: Using Table 13.5 Sprinkler spacing perpendicular t wind directin = ( ) 26,8 m = 14,7 m > 12,0 m Thus the required spacing criteria has been met. If this is nt the case then anther cmbinatin f nzzle size, spacing r perating pressure shuld be selected.

15 Sprinkler Irrigatin Grss applicatin-rate The average rate at which the water is theretically applied by the sprinkler t the wetted area is knwn as the grss applicatin rate. Each sil has a knwn ability t sak up water, which is generally knwn as the infiltratin rate f a sil. An applicatin rate higher than infiltratin rate will result in runff and inadequate misture replacement. Generally sprinklers give an applicatin rate f between 6 t 9 mm/h which mst sils can handle and gives the highest distributin efficiency. Whenever there is dubt, the sil capabilities must be tested befre deciding n an applicatin rate q GAR = L L e d e (13.2) where GAR = grss applicatin rate [mm/h] q e = sprinkler discharge [m 3 /h] L e = sprinkler spacing [m] = lateral spacing [m] L d Example 13.3: Assume the fllwing: Sprinkler discharge = 1,94 m 3 /h Sprinkler spacing = 18 m Lateral spacing = 18 m Slutin: Using equatin 13.2 GAR = (( 1, ) ( )) = 6 mm The fllwing table illustrates the abve cncept:

16 13.14 Irrigatin Design Manual Table 13.6: Discharge f sprinklers [ m 3 /h] Spacing [ m m ] Grss applicatin rate[ mm/h] x 6 6 x 9 6 x 12 6 x 15 6 x 18 9 x 9 9 x 12 9 x 15 9 x x x x x x x 18 0,11 0,16 0,22 0,27 0,32 0,24 0,32 0,41 0,49 0,43 0,54 0,65 0,68 0,81 0,97 0,14 0,22 0,29 0,36 0,43 0,32 0,43 0,54 0,65 0,58 0,72 0,86 0,90 1,08 1,30 0,18 0,27 0,36 0,45 0,54 0,41 0,54 0,68 0,81 0,72 0,90 1,08 1,13 1,35 1,62 0,22 0,32 0,43 0,54 0,65 0,49 0,65 0,81 0,97 0,86 1,08 1,30 1,35 1,62 1,94 0,25 0,38 0,50 0,63 0,76 0,58 0,76 0,95 1,13 1,01 1,26 1,51 1,58 1,89 2,27 0,29 0,43 0,58 0,72 0,86 0,65 0,86 1,08 1,30 1,15 1,44 1,73 1,80 2,16 2,59 0,32 0,49 0,65 0,81 0,97 0,73 0,97 1,22 1,46 1,30 1,62 1,94 2,03 2,43 2,92 0,36 0,54 0,72 0,90 1,08 0,81 1,08 1,35 1,62 1,44 1,80 2,16 2,25 2,70 3,24 0,40 0,59 0,79 0,99 1,19 0,89 1,19 1,49 1,78 1,58 1,98 2,38 2,48 2,97 3,56 0,43 0,65 0,86 1,08 1,30 0,97 1,30 1,62 1,94 1,73 2,16 2,59 2,70 3,24 3, Evapratin lsses The metric Frst Schwalen nmgram belw indicates that lsses increase with increase in pressure, temperature and windspeed, hwever, lsses als increase with a decrease in relative humidity and sprinkler nzzle sizes. Analysis f wind, temperature and humidity indicate that if irrigatin ccurs during sunlight hurs the lsses will seldm exceed an average f 15% ver the seasn. Hwever, lsses can be expected t be as high as 40% n certain days. If irrigatin is dne at night, the lsses will hardly exceed 5%, while lsses ver 24 hurs shuld nt exceed 10%. Trials indicated that mre than half f the daily lsses ccur between 10:00 and 16:00. Althugh it appears that half f the water is blwn away, the spray cntributes t decreased transpiratin in the plants reached. Therefre all is nt lst and a significant amunt is still effective.

17 Sprinkler Irrigatin Example 13.4: Values given: (a) Relative humidity = 10% (b) Air temperature = 32C (c) Nzzle diameter = 4,8 mm (d) Wrking pressure = 30 m (e) Wind velcity = 8 km/h Figure 13.10: Frst-Schwalen nmgram (6) Slutin: Using Figure 13.9 values a and b n scales (1) and (2) respectively, a pint can be lcated n scale (3). With this value and value c n scale (5), pint A can be fixed n pivt (4). Using values e and d n scales (9) and (7) respectively a pint B can be fixed n pivt (8). Cnnect A n pivt (4) and B n pivt (8) intersecting scale (6), t btain the percent evapratin lss. This is ± 8%. 4.5 Chice f sprinkler Sprinkler discharge [m 3 /h] and cefficient f unifrmity (CU) is dependant n the pressure [m] and nzzle size [mm]. A sprinkler is chsen t give an applicatin rate at a specific spacing with a cefficient f unifrmity f higher than 84%. Sprinkler specificatins are available in manufacturer tables. Remember that high pressure means high energy csts and applicatin rates. While larger spacings mean lw capital utlay and lw applicatin rates. Thus a cmbinatin must be chsen that gives the grss applicatin at a lw ttal cst.

18 13.16 Irrigatin Design Manual 4.6 Layut plan The lcality and size f land will determine the ptimum psitin f the undergrund and abve grund pipes. Generally the fllwing requirements shuld be strived fr: Psitin main line parallel with slpe. Psitin laterals as clse as pssible n the cnturs. Keep laterals < 80 mm in diameter, s as t make handling easy n a quick-cupling system. Try t keep laterals n either side f the main line, thus saving time and keeping the distributin f mvement f laterals simple. Always keep in mind any further extensin that culd take place. Keep lateral lengths cnstant if pssible. With prtable schemes, keep the lateral pipes ne diameter r maximum tw diameters, frm a management pint f view. The diameter f main, sub-main and lateral pipelines must be chsen crrectly t avid excessive frictin lsses and high running csts. Labur availability, cst and managerial requirement shuld be assessed befre designing a system. Often the layut f a system will be simple, as in the case f small regularly shaped areas. On the ther hand, large dd-shaped tracts with brken tpgraphy may present a full-scale cmplex engineering prblem requiring alternate layuts and careful pipe size analyses. The variatin in the number f sprinklers perating frm time t time during irrigatin shuld be kept t a minimum t facilitate lateral ruting and t maintain a near cnstant lad n the pumping plant. T btain near unifrm applicatin f water thrughut the length f a lateral line, the lines must be s lcated and must be f a pipe size and length that will result in a minimum variatin in the discharge f individual sprinklers alng the line. This variatin in discharge shuld nt exceed 10%. Lateral lines must be such that the ttal lsses in the line, due t bth frictin head and static head, will nt exceed 20% f the design perating pressure fr the sprinkler. Where a chice in lcatin f the water supply surce is t be made, the surce shuld be as near as pssible t the centre f the design area. 5 Design f sprinkler irrigatin 5.1 Design prcedures The prcedure nrmally used in planning a sprinkler irrigatin system is as fllws: Make an inventry f available resurces and perating cnditins. Include infrmatin f sils, tpgraphy, water supply, surce f pwer, crps, sil cnservatin requirements and farm peratin schedules. Determine frm lcal cnditins, the depth r quantity f water t be applied at each irrigatin, design frequency f irrigatin r shrtest irrigatin perid. Determine capacity requirements f the system. Determine ptimum water applicatin rate. Maximum (nt necessary ptimum) rates are btainable. Determine type f sprinkler required. Determine sprinkler spacing, discharge, nzzle sizes, and perating pressure fr the ptimum water applicatin rate. Determine number f sprinklers, perating simultaneusly, required t meet system capacity requirements.

19 Sprinkler Irrigatin Determine the best layut f main and lateral lines fr simultaneus peratin f the required number f sprinklers. Make necessary final adjustments t meet layut cnditins. Determine required sizes f lateral pipeline. Determine maximum ttal pressure required fr individual lateral lines. Determine required sizes f main line pipe. Check main line pipe sizes fr pwer ecnmy. Determine maximum and minimum perating cnditins. Select pump and pwer unit fr maximum perating efficiency within range f perating cnditins. Prepare plans, schedules, and instructins fr prper layut and peratin. 5.2 Design The design prcedures will be explained by means f a running example Required infrmatin Example 13.5: The farm is situated in the Munt Currie area. The crp t be grwn is pastures. The area t be irrigated = 14 ha. The farmer wuld like t irrigate by using a drag-line system. The system efficiency ( s ) = 80%. Sil: Basic infiltratin rate = 10 mm/h Water hlding capacity (WHC) (-10 t kpa) = 100 mm/m Class A-pan peak evapratin rate ( E ) = 5,80 mm/day Crp factr () = 0,7 Rainfall (R) = 0 mm Effective rainfall ( R e ) = 0 mm Percentage Allwable Water Depletin () = 50% Natural rt depth (NRD) = 0,3 m Effective sil depth (ESD) = 1,0 m Effective rt depth (ERD) = 0,3 m The average wind speed = 14 km/h

20 13.18 Irrigatin Design Manual Site plan

21 Sprinkler Irrigatin Evaptranspiratin This is the lss f water thrugh transpiratin f the grwing plant plus evapratin frm the sil surface. ET E f (13.3) where ET = evaptranspiratin [ mm/day ] E = class A-pan peak evapratin rate [ mm/day ] f = crp factr Example 13.5: ( cntinue) Frm equatin 13.3 ET = 5,8 0,7 = 4,1 mm/day Readily available water This is the depth f sil water available within the effective rt depth f a given crp under given sil and climatic cnditins and allwing unrestricted evaptranspiratin and crp grwth. RAW = WHC ERD 1000 (13.4) where RAW = readily available water [mm] WHC = water hlding capacity [mm/m] ERD = effective rting depth [m] = percentage allwable water depletin [%] Example 13.5: ( cntinue) Frm equatin 13.4 RAW = (100 0,3 (50 100)) = 15 mm Nett irrigatin requirement The depth f irrigatin water necessary t meet evaptranspiratin f the crp during a certain perid and in a specific grwing phase f the crp. NIR = ET R e (13.5) where NIR = nett irrigatin requirement [mm/day] ET = evaptranspiratin [mm/day] = effective rainfall [mm/day] R e Frm equatin 13.5 NIR = 4,1-0 = 4,1 mm/day

22 13.20 Irrigatin Design Manual Grss irrigatin requirement Nett irrigatin requirement f a given crp plus peratinal lsses f the system. 100 NIR GIR = s (13.6) where GIR = grss irrigatin requirement [mm/day] NIR = net irrigatin requirement [mm] s = system efficiency [%] Frm equatin 13.6 GIR = ((100 4,1) 80) = 5,1 mm/day Cycle length The actual time lapse between the cmmencement f tw successive applicatins fr a specific irrigatin set. The sil is a reservir that stres water fr the plant. The plant uses the water each day ut f the reservir at a certain rate, thus at maximum use wuld nly be available fr s many days. RAW t c = NIR (13.7) where t c = cycle length [ days] RAW = readily available water [mm] NIR = net irrigatin requirement [mm/day] Frm equatin 13.7 t c = 15 4,1 = 3,7 days Hwever, it is nt pssible t wrk in parts f a day unless the system is cmputerised r has tp management input. It is suggested that a practical cycle length be chsen, such as 3,5 days Area cvered per sprinkler As a general rule ne wuld use a sprinkler spacing f m in areas where the average maximum wind velcity is < 13 km/h. In areas where the average maximum wind velcity is > 13 km/h a spacing f m wuld be used. In gravity irrigatin schemes the spacing between sprinklers will depend upn the pressure available in the scheme.

23 Sprinkler Irrigatin A = L e L d (13.8) where A = wetted area [m 2 ] L e = lateral spacing [m] L d = sprinkler spacing [m] Frm equatin 13.8 As the wind speed is 14 km/h, a m spacing will be used. A = = 144 m Chice f sprinkler Generally sprinklers give an applicatin rate f between 6 t 9 mm/h which mst sils can handle and give the highest distributin efficiency. q e GAR A (13.9) where q e = sprinkler discharge [/h] GAR = grss applicatin rate [mm/h] A = wetted area [m²] Frm equatin 13.9 Chse an applicatin rate f 6 mm/h, as it must be less than the final infiltratin rate f the sil (10 mm/h). q e = = 864 /h 0,86 m³/h At this stage ne wuld refer t a manufacture s sprinkler perfrmance table t chse a specific sprinkler package. (i.e. nzzle size, ptimum perating pressure and diameter f the wetted area). As per dealer specificatins use the sprinkler ABC 9/64" nzzle perating at 25 m. q e = 0,85 m³/h Grss applicatin rate The rate at which the water is theretically applied by the sprinkler t the wetted area. An applicatin rate higher than the infiltratin rate f the sil will result in runff and inadequate water replacement. qe GAR A (13.10) where GAR = grss applicatin rate [mm/h] q e = discharge per sprinkler [m 3 /h] A = wetted area [m 2 ]

24 13.22 Irrigatin Design Manual Frm equatin GAR = ((0, ) 144) = 5,9 mm/h Nte: Applicatin-rate must be less than final infiltratin rate f sil. If this is nt the case then anther sprinkler package must be chsen. 5,9 mm/h < 10 mm/h Therefre the grss applicatin rate is fine Nett applicatin rate The rate at which the water is applied t the sil surface by the sprinkler after taking int accunt the applicatin efficiency f the system. NAR = GAR a (13.11) where NAR = nett applicatin rate [mm/h] GAR = grss applicatin rate [mm/h] a = applicatin efficiency [%] Frm equatin Assume applicatin efficiency at 80% NAR = (5,9 (80 100)) = 4,7 mm/h Standing time The calculated perid f time fr which a system has t irrigate t apply the design applicatin. The design applicatin being the maximum applicatin fr which the system is designed. RAW t s = NAR (13.12) where t s = stand time [h] RAW = readily available water [mm] NAR = net applicatin rate [mm/h] Frm equatin t s = 15 4,7 = 3,2 hurs Fr practically reasns use a 3 hur stand time Number f sets per day The farmer is usually asked by the designer hw many days in a week and hurs in a day he wuld like t irrigate his lands. Assume a 4 sets per day sequence, as this wuld fit int the number f perating hurs per day.

25 Sprinkler Irrigatin Wrking hurs per day th=ts n ( ) where t h = wrking hurs per day [hrs] t s = stand time [hrs] n = sets per day Frm equatin t h = t s n = 3 4 =12 h Number f sets per cycle The number f psitins t which a sprinkler is mved during an irrigatin cycle is dependant upn: the number f wrking days in a cycle the number f stands per day als the answer t the abve questins can have a great influence n the cst f a scheme n c = nt s (13.14) where n c = number f sets per cycle t c = cycle length [days] n = sets per day Frm equatin n c = n t c = 4 3,5 = Grss applicatin per cycle This is calculated accrding t the daily crp requirement and the cycle length. GA = GIR t c (13.15) where GA = grss applicatin per cycle [mm] GIR = grss irrigatin requirement [mm/day] t c = cycle length [days] Frm equatin GA = 5,1 3, 5 = 17,9 mm

26 13.24 Irrigatin Design Manual Number f sprinklers perating simultaneusly This determines the number f sprinklers perating. A10000 N (13.16 ) e n L L where N e = number f sprinklers A = area f irrigatin [ha] n c = sets per cycle L d = lateral spacing [m] = sprinkler spacing [m] L e Nte: 1 ha = m 2 c e d Frm equatin N e > (( ) ( ) ) > 69 The shape f the land will influence the number f sprinklers perating simultaneusly, sme sprinklers might nly be used a few times during a cycle. There are 66 sprinklers required. (See layut plan ) System capacity This is the required pumping rate f the irrigatin system, accrding t the maximum number f sprinklers perating simultaneusly. Q N e q e (13.17) where Q = system capacity [m 3 /h] N e = number f sprinklers q e = sprinkler discharge [ m 3 /h] Frm equatin Q = 66 0,85 = 56,1 m 3 /h Layut plan The terrain, slpe f the land, radways, fences and ther bstacles wuld influence the layut f an irrigatin system. In this example the fllwing has been taken int accunt: The laterals t run parallel t the cnturs s as t restrict height differences as much as pssible. Tw identical systems f 33 sprinklers each t perate ff tw sub-main lines, which in turn are linked t a cmmn main line. The idea f tw identical systems is s as t limit the length f the laterals, as the ttal width f the land is ± 550 m.

27 Sprinkler Irrigatin 13.25

28 Sprinkler irrigatin systems Hydraulic calculatins This is the hydraulic design f the system, frm the sprinkler stand pipe t the junctin with the main line. Imprtant pints: The pipe frictin frmula's are applicable t "clean" pipes. The chice f cnnectin between laterals and main line, as sme flw path areas are small which result in high frictin lsses. The cnstants used in frictin lss calculatins, must be referred t Chapter 6: Pipe hydraulics. 6.1 Stand pipe 2, = di -10 hfs 4,87 q 1,85 e (13.18) where h fs = frictin lss in stand pipe [m] = stand pipe length [m] q e = flw rate [m 3 /h] d i = internal pipe diameter [m] Frm equatin (Hazen - Williams) Assume l = 0,5 m q e = 0,85 m³/h d i = 0, m ( 21,3 mm) h fs = 2, ,5 (0,85 ) 1,85 (0, ) 4,87 = 0,01 m 6.2 Dragline hse The calculatin f the frictin lss in a dragline hse must be calculated by reading ff figures frm a frictin lss chart, which can be supplied by a manufacturer f the dragline hse. T be able t calculate the frictin lss in the dragline hse ( h fl ) the fllwing infrmatin must be knwn: dragline hse length flw rate internal diameter f pipe Assume l = 36 m q e = 0,85 m 3 /h d = 0,020 m ( 20 mm) Using a frictin lss chart supplied by the manufacturer, the frictin lss in the dragline hse ( h fl ) is calculated at 0,74 m.

29 Sprinkler Irrigatin Lateral Lateral line pipe sizes will be s chsen that the ttal pressure variatin in the line, due t frictin head and static head (if any), des nt exceed 20% f the design perating pressure f the sprinkler. Flw rate and frictin lss reductins ccur at every utlet alng a sprinkler lateral. A methd f cmputing pressure lsses in multiple utlet pipelines invlves first cmputing the frictin lss in the line withut multiple utlets and then applying a factr F t (Jensen and Fratini factr) based n the number f utlets in the line. (Refer t Chapter 6: Pipe hydraulics). An average delivery factr adf can als be applied. Frictin lss in upvc pipes. 4, = di -10 hf 4,77 Q 1,77 (13.19) where h f = frictin in pipeline [m] = length f pipe [m] Q = flw rate [m 3 /h] d i = internal pipe diameter [m] Frm equatin (Lamnt) Lateral F - P Assume l = 126 m Q = 9,35 m³/h d = 0,046 1 m ( 46,1 mm - nminal diameter 50 mm) F t = 0, , (9,35 ) = (0,046 ) = 7,04 m h f 4,77 1,77 adf is the average delivery factr as set ut belw: 0,77 fr a lateral with ne diameter 0,63 fr a lateral with tw diameters 0,50 fr a lateral with three r mre diameters Thus frictin lss in the lateral pipe h f = hf F t adf = 7,04 0,382 0,63 = 1,69 m H = h e + h m + h s + h f (13.20) where H = pressure required at main line h e = average design perating pressure h m = stand pipe height h s = pressure required t vercme elevatin h f = allwable pressure lss due t frictin in stand pipe, dragline hse and lateral

30 13.28 Irrigatin Design Manual Lateral F-P laid dwnhill Pressure required at last hydrmatic valve is: H = ((25 + 0,5 + (0,01 + 0,74 )) = 26,25 m * Frm equatin As the lateral F-P is running dwnhill, h s is entered as a negative (-). Pressure required at the main line is: H = ((25 + 0,5 + ( - 0,55 ) + (0,01 + 0,74 + 1,69)) = 27,39 m ** Anther methd f cmputing pressure lsses in multiple utlet pipelines invlves a simple spreadsheet prgramme, where frictin is calculated in each sectin f pipe between utlets. The ttal frictin lss will be the accumulative frictin lss f each sectin alng the lateral pipeline. Example: Lateral F-P (dwnhill) Outlet number Length [m] Ttal Length [m] Discharge Flw [m 3 /s] Pipe diameter [mm] Lateral pipe frictin [m] Static height [m] Ttal head [m] ,00 126,00 114,00 102,00 90,00 78,00 66,00 54,00 42,00 30,00 18,00 6,00 0,85 1,70 2,55 3,40 4,25 5,10 5,95 6,80 7,65 8,50 9,35 46,10 46,10 46,10 46,10 46,10 58,90 58,90 58,90 58,90 58,90 58,90 0,01 0,03 0,07 0,11 0,17 0,07 0,09 0,12 0,15 0,18 0,10-0,05-0,05-0,05-0,05-0,05-0,05-0,05-0,05-0,05-0,05-0,05 26,25* 26,21 26,19 26,21 26,27 26,39 26,41 26,45 26,52 26,62 26,75 26,80** TOTAL 1,10-0,55 ** pressure at main line. The difference is due t the difference in ttal frictin lss alng the lateral. The reasn fr the differences is that 1,69 m is calculated using average pipe diameter and factrs. where clumn 1 = the sprinkler utlets numbered alng the length f pipe clumn 2 = length f each sectin f pipe clumn 3 = accumulative length f lateral pipe clumn 4 = ttal flw rate in each sectin f lateral pipe clumn 5 = internal pipe diameter clumn 6 = frictin in each sectin f pipe accrding t equatin clumn 7 = static height difference alng each sectin f pipe, measured in the field. clumn 8 = pressure required at main line (clumn 8 + clumn 6 + clumn 7 ) Lateral J-Q laid uphill Frm equatin Pressure required at the main line is: H = ((25 + 0,5 + 0,66 + (0,01 + 0,74 + 1,69)) = 28,60 m **

31 Sprinkler Irrigatin Example: Lateral J-Q (uphill) Outlet number Length [m] Ttal Length [m] Discharge Flw [m 3 /s] Pipe diameter [mm] Lateral pipe frictin [m] Static height (±)[m] Ttal head [m] ,00 126,00 114,00 102,00 90,00 78,00 66,00 54,00 42,00 30,00 18,00 6,00 0,35 1,70 2,55 3,40 4,25 5,10 5,95 6,80 7,65 8,50 9,35 46,10 46,10 46,10 46,10 46,10 58,90 58,90 58,90 58,90 58,90 58,90 0,01 0,03 0,07 0,11 0,17 0,07 0,09 0,12 0,15 0,18 0,10 0,06 0,06 0,06 0,06 0,06 0,06 0,06 0,06 0,06 0,06 0,06 26,25* 26,32 26,41 26,54 26,71 26,94 27,07 27,22 27,40 27,61 27,85 28,01** TOTAL 1,10 0,66 ** pressure at the main line. The reasn fr the difference as already explained. 6.4 Pipe cuplings Cuplings withut utlets h fk n k v = 2 g 2 (13.21) where h fk = frictin lss in pipe cuplings [m] n = number f cuplings v = average velcity ver pipe length [m/s] k = cupling cefficient g = gravitatinal cnstant [m/s 2 ] Table 13.7: Typical values fr k Nminal pipe diameter [mm] k 50 0,64-1,3 80 0,18-0, ,05-0, ,04-0,26 Fr lateral F-P Frm equatin Assume n = 11 r = pipe radius = 0,046 1 m k = 0,64 Q = 9,35 m 3 /h

32 13.30 Irrigatin Design Manual v = Q A (13.22) where v = velcity in pipe [m/s] Q = flw rate [m 3 /h] A = area f pipe [m 2 ] (i.e. r 2 ) Frm equatin v = (( 9,35 ( 0, )) = 1400,4 m/h = 0,4 m/s Frm equatin h fk = (( 11 0,64 0,4 2 ) ( 2 10 )) = 0,06 m 6.5 Other pipe fittings h fp kc v = 2 g 2 (13.23) where h fp = frictin lss in fittings [m] k c = frictinal cefficient (varies accrding t fittings) v = water velcity [m/s] g = gravitatinal cnstant [m/s 2 ] Generally a figure f 5% f the ttal frictin lss f the system is added t the calculated figure t cver fr lsses in fittings. Test all cases where yu have dubt.

33 6.6 Final plan Sprinkler Irrigatin 13.31

34 13.32 Irrigatin Design Manual 7 Side-rll system General A side-rll system is the mechanized system that cmpares mst with cnventinal sprinkler irrigatin. The management f the system is als basically the same as fr a cnventinal system, except that an entire lateral can be shifted in ne actin, instead f pipe fr pipe. The system is ideal fr rectangular fields, smaller than 20 ha, if nly lw-grwing crps, such as ptates r grazing crps are cultivated. The system basically cnsists f an aluminium pipeline, munted n wheels as such that the pipeline acts as an axle. The machine is built up frm 12 m pipes each with a wheel in the center and a sprinkler as well as a drainage valve at the end (see Chapter 10: Irrigatin systems fr an illustratin f the system) The sprinkler is munted t a bearing with a weight that always pulls it in a vertical psitin, regardless f the angle that the pipe makes with the utlet. It is therefre nt necessary t shift the lateral s that the sprinklers are in the tp psitin. The fllwing mdels are available, namely: Self-driven mdel (1,0 m crp free-height) A small petrl engine with hydraulic prpelling mechanism is placed n a fur-wheel cart in the center f the field. A 6 m pipe with a sprinkler munted at the furthest end, is placed n bth sides f the cart. The 12 m pipe with a wheel in the centre is nw attached until the required machine length is built up. Manual mdel (1,9 m crp free-height) In this case, the cart is replaced with a pedal unit. The unit basically cnsists f tw wheels placed clse tgether and cnnected t each ther with hrizntal rds n the circumference. The system is shifted by a persn climbing n the pedal unit, s that his weight makes the machine rll. Bth mdels are available with side inlet r center inlet. Basic peratin The biggest difference between a side-rll system and mst ther mechanized systems is that it stands still while irrigatin is taking place. As sn as the water is switched ff, the machine dries and shifts t the next psitin. The system is usually designed fr a spacing f m (12 m between sprinklers and 18 m between standing psitins). The machine stands in ne psitin and irrigates fr a perid f 4 11½ hurs, depending n the design. The water supply is then cut, the machine drains and is shifted t the next psitin. The water supply is switched n and the prcess is repeated. Management It is imprtant t use as high as pssible an applicatin temp, because it enlarges the surface that the machine can handle and reduces capital csts f the system. The infiltratin capacity f the sil must hwever nt be exceeded. If the slpe is at an incline n the mvement directin f the machine, the machine can lse its tracking and must be placed back n its track with hand labur. The fields must therefre preferably have a flattish slpe ver the machine length.

35 Sprinkler Irrigatin Try and mve the machine parallel t the crp rws. Cultivatin f the sil can then take place during irrigatin. D nt mve the machine while the pipes are full f water. Design The fllwing guidelines can be used: Make an inventry f available resurces. Sil: Area available, quality, depth, infiltratin rate and water hlding capacity. Water: Amunt available, at what rate and quality. Crp: Farming practice and water requirements. Management: Wrking hurs per day and number f days per week. Design specificatins Calculate the irrigatin requirement [mm/day], grss applicatin, cycle, stand time and determine what areas with the available water can be irrigated. Layut f system Try t fit in machine and main line as ecnmically in the land. Chice f sprinkler Chse spacing and discharge t fit in with infiltratin rate and wind cnditins. System capacity Calculate the number f sprinklers per machine and number f machines test system capacity against water availability. Pressure Calculate frictin and test if pressure is within the nrmal ± 20% maximum range. The fllwing equatin can be used t determine the inlet pressure at the beginning f the lateral. h in = h e + h s + h f (13.22) where h in = inlet pressure at beginning f lateral [m] h e = sprinkler pressure [m] h s = static height difference t highest pint [m] h f = frictin thrugh machine [m] The hydrant pressure can be calculated as fllws: h n = h in + h m + h fi (13.23)

36 13.34 Irrigatin Design Manual where h n = hydrant pressure [m] h m = height f machine [m] h fi = frictin in rubber supply line [m] The pressure must nw be tested t see if it is within the nrms. Pr essure difference between first and last sprinkler Inlet pressure at begin f lateral = hf + hs h + h + h e f s Hydrant spacing Try and perate 5 psitins frm ne hydrant. Main line design (Chapter 6 Hydraulics) Pump design (Chapter 16: Pumps) Example 13.6: Area f land = m (9 ha) Crp : Lucern with net irrigatin requirement = 7 mm/day Water hlding capacity f sil = 120 mm/m Rt depth = 0,9 m Allwable % depletin = 50% Infiltratin rate = 10 mm/h Brehle delivery = 40 m³/h System efficiency = 80% The farmer is prepared t mve the machine twice daily n a 6 day cycle. He prefers a maximum f 18 m hydrant spacing. Slutin : Readily available water fr crp at 50 % depletin = 120 0,9 0,5 = 54 mm Irrigatin per cycle = 54 mm effective Cycle length = (54 7) = 7,7 days Hwever it is practical t wrk n a 7 day cycle Nett applicatin = ((54 ( 7 7,7)) = 49 mm Grss applicatin = (49 0,8) = 61 mm Irrigatin f 61 mm must be applied every 7 days Standing time (given) = 11 hurs Maximum area that can be irrigated A = = 8,65 ha < 9 ha Therefre nly 8,65 ha can be irrigated

37 Sprinkler Irrigatin Layut Sprinkler spacing = 12 m Operating spacing = 18 m Number f mves per cycle length = settings per day wrking days Length f land = = 216 m (f the 300 m available) Machine length = 300 m (25 spans - 26 sprinklers) Wetted area = = 6.74 ha < 8.65 ha Chse maximum dragline pipe length = 20 m Prpsed hydrant spacing = 40 m Number f hydrants = (216 40) = 5,4 Chse 6 hydrants Therefre hydrant spacing = (216 6) = 36 m and dragline length = 18 m Sprinkler chice Applicatin rate = (61 11) = 5,55 mm/h < infiltratin rate Sprinkler discharge = ((5, ) (1000)) = 1,2 m³/h Chse nw a sprinkler frm the manufacturer s catalgue. System capacity There are 26 sprinklers munted n the machine Q = 26 1,2 = 31,2 m³/h Equatin fr the theretical flw rate (equatin 14.1): 61 6,74 10 Q = = 31,2 m /h Machine pressure Calculate frictin lss in the pipes accrding t Chapter 6: Pipe hydraulics and use equatin t determine the inlet pressure at the beginning f the lateral.