LELABSINES
Case study

A well, no basin: direct solar
irrigation in Senegal

In Pout, in the Thiès region, a community of growers wants to switch its market gardening to solar. One of them opens his 5-hectare field as a pilot plot: a 30 m well, no reservoir or basin, and a clear request, a direct supply of 30 m³ per day. Here is how this solar irrigation project is built in LE LAB, the solar pumping sizing application, with real screenshots and figures.

Pout, Thiès region · Senegal 5 ha pilot field 30 m well Target: 30 m³/day Direct supply, no reservoir
The project

The need, as the client expresses it

The first client of a collective venture: if the pilot plot convinces, the other growers will follow. The brief fits in three lines: pump from the 30 m well, water directly without going through a basin, and target 30 m³ per day. No backup, no storage: the field drinks at the pace of the sun.

30 m³/daythe target requested, year-round: enough to drip-irrigate a little under one hectare at the height of the dry season
30 mthe well depth, pump set at around 25 m; the water level and well yield will be measured on site
0 reservoirthe client's deliberate choice: direct irrigation, with no buffer basin
5 hathe pilot plot's field, to be equipped in stages

The figure to face head-on: 30 m³ per day will not irrigate 5 hectares of market gardening in the dry season. It will irrigate a fraction of it, and that is precisely the spirit of a pilot plot: prove the principle on the first block, then expand the solar array once the community commits.

Step 1

The input data in LE LAB

A few minutes of input. The solar reference city is Dakar, around fifty kilometres from Pout. The pump is set at around 25 m in the 30 m well, the delivery head to the irrigation network is low and the field-head pipe is taken at 100 m. The total head is calculated automatically: 33 m. And to the water reserve question, the client's answer is respected: none.

Study summary in LE LAB: Dakar, 30 m³ per day year-round, depth 25 m, delivery head 2 m, 100 m of pipe, calculated TDH 33 m, no electrical backup, no water reserve

The summary before calculation: nine answers are enough, the total dynamic head is calculated for you.

Step 2

What LE LAB proposes

A GRUNDFOS SQF 5A-7, powered by 3 panels of 450 Wp, for 1,350 Wp in a single string. Average production: 34.8 m³ per day, from 29.5 in August to 40.2 at the height of the dry season. LE LAB is multi-brand: the study scans the catalogue and selects the pump whose curves fit the project's operating point, here an SQFlex, Grundfos's solar range.

Solution proposed by LE LAB: GRUNDFOS SQF 5A-7 pump, 1350 Wp solar array with 3 panels of 450 Wp, average production 34.8 m³ per day

The solution at a glance: pump, solar array and average production.

Why an SQFlex here? The range is built for this kind of site: the motor accepts direct current from the solar array as well as the alternating current of a generator if the project evolves, and dry-run protection is standard. On a village well whose yield still needs to be confirmed by a pumping test, this protection is not a detail: the pump stops itself if the level drops too far, and restarts once the well has caught its breath.
Step 3

Production, month by month: a red bar that falls in a good spot

Monthly production is read against the need, over sixteen years of the region's real solar data. Eleven months stay above the 30 m³ line. The only one that misses the target is August: 29.5 m³ per day, within 2%. And the rainfall curve tells why this dip does no harm: August is the heart of the rainy season, 191 mm of rain, the month when the sky irrigates instead of the pump. Market gardening in Pout, meanwhile, peaks in the dry season, when production runs between 34 and 40 m³.

Estimated monthly production against the need of 30 m³ per day: only August falls under the line at 29.5 m³ per day, at the peak of 191 mm rainfall

The critical month is shown in red, not hidden: August, 29.5 m³/day for 30 required, under 191 mm of rain. The blue line is monthly rainfall.

Step 4

The typical day: watering at the rhythm of the sun

With no basin, daily output becomes the grower's working tool: it dictates when the water flows. The typical day shows a plateau from 10 am to 3 pm around 4 m³/h, with a peak at 4.5 m³/h: watering rotations are scheduled around this window, and drip irrigation does the rest. In July, the month the rainy season begins, the day produces 30.2 m³: the need is covered with a 1% margin, right at the edge.

Daily output for a typical day in July: hour-by-hour flow rate, peak at 4.5 m³/h, 30.2 m³ produced, need of 30 m³ covered with 1% margin

The typical July day, hour by hour: the midday plateau is the irrigation window.

Step 5

No reservoir: coverage, quantified

The choice of direct supply is respected, and its price is shown. Without a water reserve, the installation covers the need in full 305 days out of 365. On the other 60 days, the pump still delivers 78% of the need on average, and only one day a year falls below 20%. The chart shows where these days concentrate: July, August, September, the rainy season, precisely when the rain takes over.

Need coverage block with no water reserve: 305 of 365 days fully covered, the other 60 days deliver 78% of the need, incomplete days concentrated from July to September

A benchmark is given too: 25% more panels would raise coverage to around 340 days out of 365. And if a basin enters the project one day, LE LAB simulates it on demand.

Fully solar pumping owns its rule. Water is stored, not electricity: no batteries to buy or replace. In direct irrigation, the crop itself absorbs the swings: a grey day delivers 78% of the water, and the soil and mulching buffer the rest. It is a trade-off market gardening tolerates far better than a village water tower.
Step 6

Manufacturer curves, at the real operating point

The pump's Q/H curves, plotted from official GRUNDFOS data, with the project's head highlighted: 5.5 m³/h at full power on the 33 m curve. The pump accepts up to 9 m³/h and 50 m of head: the system works at the heart of its range, a guarantee of longevity.

Manufacturer curves for the GRUNDFOS SQF 5A-7 pump: flow according to available power by head, operating point 5.5 m³/h at 33 m

Flow according to available power, by head. The yellow curve is the project's, at 33 m.

What this case shows

The tool frames, the trade decides

305/365 daysgoing without a reservoir is not a gamble: it is simulated day by day and quantified before signing
78%what the pump still delivers on grey days, concentrated in the rainy season, when the rain irrigates in its place
16 yearsproduction and coverage are tested day by day over sixteen years of the region's real solar data
HonestyAugust's red bar is shown, the fraction of the field actually irrigable is stated, and the well's yield still needs to be measured before the offer

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