ANALYSIS OF CROP PATTERN PLANT AND IRRIGATION WATER NEEDS IN PAUH TINGGI IRIGATION NETWORK PLANNING, PAUH TINGGI VILLAGE, KERINCI DISTRICT, JAMBI

Pauh Tinggi irrigation network planning which has an area of irrigation land of 473 ha. This irrigation plan draws water from the Pauh Tinggi Dam located in the Batanghari Hulu river, Kerinci Regency, Jambi. Population growth which is directly proportional to the increasing necessities of life, one of which is in the food sector, has made the government take the initiative to meet the needs and welfare of the community by opening land into productive areas of rice fields and fields, and making irrigation plans. In making irrigation planning, hydrological and rainfall calculations are needed to be able to make the right cropping system for farmers in Pauh Tinggi Village, Kerinci Regency, Jambi. A calculation of 17 alternative cropping patterns with different types of plant variants and different plans for the initial planting period were carried out by comparing with the mainstay debit factor (Q80). It was found that the cropping pattern is very possible always using the RICE-RICE-CROP cropping pattern. The most efficient and optimal planting pattern is the alternative planting pattern 14 in the form of RICE -RICE-CORN with Netto Field Water Requirements in tertiary plots (NFR tertiary) ranging from 0 1.30 ltr / sec / ha with a maximum of 1.30 ltr / sec / ha in January I, while irrigation water needs in the intake (DR intake) range 0 1.60 ltr sec / ha with a maximum of 1.60 ltr / sec / ha in January I.


INTRODUCTION
Irrigation is a human effort in irrigating plants that need water, useful for growing plants to get the benefits. According to The Republic of Indonesia UU No. 7 of 1996(UU RI No.7 1996 concerning Food, states that food is a basic human need whose fulfillment is the basic right of every Indonesian people in realizing quality human resources to carry out national development.
Based on this, the Kerinci Regency Government cleared unused land into productive areas in several villages within its territory. Population growth which is directly proportional to the increasing need for living one of them in the food sector,makes the government take the initiative in meeting the needs and welfare of the community by opening land into productive areas of rice fields and fields, and making irrigation plans.
One area in Kerinci Regency that needs hydraulic analysis is the Planning of Pauh Tinggi irrigation network which has an irrigation area of 473 ha. This irrigation plan draws water from the Pauh Tinggi Dam located in the Batanghari Hulu river, Kerinci Regency, Jambi, taking into account the right and best planting patterns for the people of Pauh Tinggi Village, Kerinci Regency, Jambi.

Percolation and Seepage (P)
The rate of percolation is very dependent on the properties of the soil. Data on percolation will be obtained from soil capability studies. The soil graduation test will be part of this investigation. (KP 01, 2013) Based on the type of soil, the percolation power can be grouped into: 1. Sandy loam with percolation 3-6 mm / day 2. Loam with percolation power of 2-3 mm / day 3. Clay loam with a insulation power of 1-2 mm / day.

Land Preparation
For tertiary plots, the recommended time period for land preparation is 1.5 months. If land preparation is mainly carried out with machine tools, a period of one month can be considered. Land preparation. (KP 01, 2013) Calculation of water requirements for land preparation is done by the Van de Goor Zijlstra method. This method is based on water requirements to replace water losses due to evaporation and percolation in paddy fields that have been saturated for 30 days with a height of inundation of 250 mm, if there is a resting area of inundations of 300 mm or 8.33 mm / day. M = E0 + P = 1.1 ET0 + P .............

Water layer replacement (WLR)
After fertilization needs to be scheduled and replace the water layer as needed.
Replacement is estimated at 50 mm each month and two months after transplantation (or 3.3 mm / day).

Evapotranspiration Reference (ETo)
Reference evapotranspiration (ETo) is the value of evapotranspiration of grass plants that spread over 8-15 cm in height, actively growing with enough water, to calculate the reference evapotranspiration (ETo), several methods can be used, namely: 1. Penman method, 2. the evaporation pan method 3. radiation method, 4. Blaney Criddle and method 5. Penman modification method FAO (Suyono, 2003). Estimating the magnitude of crop evapotranspiration there are several stages that must be carried out, namely suspecting reference evapotranspiration; determine the coefficient of the plant then pay attention to local environmental conditions; such as climate variations at any time, altitude, land area, available groundwater, salinity, irrigation methods, and agricultural cultivation. Some methods for estimating reference evapotranspiration:

Penman Modification Method
The method used here is the Penman Modification method. To calculate ET0 using the Penman modification method, the formulas used are:

Mainstay Discharge
Mainstay discharge is a reliable debit for a certain level of reliability or reliability. For irrigation purposes, reliable discharge is used with 80% reliability as specified in the Irrigation Planning Criteria. This means that 80% of the possible discharges that occur are greater or equal to the debit, or in other words, the irrigation system may fail once in five years. For the needs of drinking water and industry, higher reliability is required, which is around 90% to 95%. If the river water is used for hydroelectric power generation, very high reliability is needed, which is between 95% to 99% (Kementerian PUPR Ditjen Sumber Daya Air, 2017).

Mainstay Debit Calculation
In this study the mainstay discharge analysis using FJ.Mock with the concept of water balance based on the 1973 hydrological cycle. Basically, the FJ Mock method is an analysis of the balance of monthly water discharge based on data on semi-monthly rainfall, evapotranspiration, soil moisture and groundwater storage. Some of them are lost due to evapotranspiration, some of them immediately turn into direct runoffs and some go into the ground or infiltrate. Where infiltration first saturates the surface of the ground then water percolation occurs and comes out as base flow. We can see the dependence between falling rainfall and evapotranspiration, infiltration, and total runoff which is a component of discharge.
The data or assumptions used in the FJ Mock calculation are: A. 10-year Rainfall Data with rainfall stations which are considered to represent the condition of the area. The data needed is: a) d average: 10-year average rainfall b) n: Average number of 10 annual rainy days (Agustin, 2011) B. Restricted evapotranspiration is actual evapotranspiration by comparing the condition of vegetation and land surface and rainfall frequency. a) Evapotranspiration (ET0) using the Penman Modification method (mm / day) b) Land opening factors used are: -M 0% for land with dense forest -M 10-40% for eroded land -M 30-50% for agricultural land though c) E = ET0 x (m / 20 (18 -n) (Agustin, 2011) The probability of being fulfilled is set at 80% (the possibility that the river discharge is lower than the main discharge is 20%). That possibility uses calculations Q mainstay 80% = (0.8 x Mainstay Debit) / (area DI) ltr / sec / ha .. (II.35) Water balance = Q mainstay 80% -DR intake …… (II.36)

Irrigation Efficiency
According in general water losses in irrigation networks can be divided as follows. a. 12.5% -20% in tertiary channels b. 5% -10% in the secondary channel c. 5% -10% in the primary canal (KP 03, 2013) Efficiency in each plot is estimated as follows: • Efficiency values in primary plots ranged from 92.5% -87.5%.
• Efficiency values in secondary plots range from 92.5% -87.5% • Efficiency values in tertiary plots range from 85% -77.5%. (KP 01, 2013) Irrigation Water Needs Irrigation water demand is the amount of water volume needed to meet the needs of evapotranspiration, water loss, water needs for plants by paying attention to the amount of water provided by nature through rain and the contribution of groundwater. (Sidharta, 1997) The need for water in paddy fields for rice is determined by the following factors: 1. how to prepare the land 2. water requirements for plants 3. percolation and seepage 4. Substitution of water layers, and 5. effective rainfall. The total water demand in a paddy field (GFR) includes factors 1 to 4. The net (net) demand for water in a paddy field (NFR) also takes into account effective rainfall. Calculation of irrigation water needs (NFR) can be done with the formula: Rice NFR = ETC + Pd + P + WLR -Re ...... (II.37) NFR palawija / sugarcane = ETC -Re ............

Netto Debit
To determine the dimensions of the channel, the planned capacity is calculated against the maximum discharge Q = 100% x Maximum. The discharge plan for a channel is calculated using the following general formula (

Data Management Stage
This irrigation analysis stage includes: a) Identification of problems and criteria b) Secondary data collection c) Analysis of climatological and hydrological data d) Calculation of cropping patterns e) Calculation of plant water requirements, and efficiency f) Calculation of efficiency g) Mainstay debit calculation

Planning Data
Each analysis requires data as a settlement to be carried out. The data is processed using the formula in accordance with the Irrigation Planning (KP) Criteria. The supporting data include:

Topographic Map
This topographic map is the topographic map of the Kerinci Regency, which was obtained from the Kerinci Regency Public Works Department. The Pauh Tinggi Irrigation Area has an area of 473 ha of irrigation land, and is divided into 12 tertiary plots. The Pauh Tinggi irrigation area receives water from the dammed Batanghari River.

Maximum Rainfall and Finding Missing Data
Looking for maximum rainfall data for the Depati Parbo and Kayu Aro areas with 2 periods per month. There was missing data in May 2013 in the Depati Parbo area, so searching for lost data was done as follows:  Then it was obtained in May 2013 in the Depati Parbo area for period I which was 14,057 mm / day and untul period II which was 13,185 mm / day.

Figure 5. R80 Mainstay Rainfall Graph
In this graph it can be concluded that the mainstay rainfall (R80) which is mostly found in October period 2 with a value of 39.0 mm / period, while the few that are found in July period  I II I II I II I II I II I II I II I II I II I II I II I II   . Effective Rainfall From this graph it can be seen that the effective rainfall for rice (Re-paddy) is the largest, and the effective rainfall for the smallest (Re-cropping). The greatest effective rainfall is in the 20th or October period 2, while the smallest effective rainfall is in the 14th or July period 2.

Calculating Potential Evapotranspiration (ET0)
The method used here is the Penman Modification method because the climatology data is quite complete. Here are the results of the count for Evapotranspiration (ET0): Calculate E (Evaporation) from the values sought for ice (saturated water vapor pressure) and ed (water vapor pressure at elevation 2 m above the surface) and value B:

Water Layers Replacement (WLR)
After fertilization needs to be scheduled and replace the water layer as needed.
Replacement is estimated at 50 mm each month and two months after transplantation (or 3.3 mm / day).

Percolation and Seepage (P)
The rate of percolation is very dependent on the properties of the soil. Data on percolation will be obtained from soil capability studies. The soil graduation test will be part of this investigation. (KP 01, 2013) Based on the type of soil in Pauh Tinggi, which is clay loam, the percolation rate is 2 mm / day.

Consumptive Water Needs (ETC)
Consumptive use is the amount of water used by plants for the photosynthesis of these plants.  4,172 4,667 4,552 4,467 3,849 3,358 3,632 4,235 8,645 3,158 4,012 3,830 2 Eo=1,1 x Eto mm/hari 4,590 5,134 5,008 4,913 4,234 3,694 3,996 4,659 9,509 3,474 4,414 4,212 3 P mm/hari 2,00 2,00 2,00 2,00 2,00 2,00 2,00 2,00 2,00 2,00 2,00 2,00 4 M =Eo +P mm/hari 6,590 7,134 7,008 6,913 6, 234 5,694 5,996 6,659 11,509 5,474 6,414 mm/hari 11,804 12,967 12,070 12,263 11,580 13,117 11,431 11,848 15,373 11,110 11,948 11,566 Kebutuhan air untuk penyapan lahan ( Metode Van de Door dan Zijlstra ) Perhitungan No. Periode  I II I II I II I II I II I II I II I II I II I II I II I  II Figure 7. Consumptive Water Needs (ETc) Graph This graph shows that the largest rate of ETC consumptive water demand was in September I with a value of 8.94 mm/day, while the lowest was in February, June, and October II with a value of 0.00 mm / day because at that time, and land preparation. As for the greatest ET0 water demand is in September I with a value of 8.6 mm/day, and the smallest in June with a value of 3.3 mm / day.

Irrigation Water Needs and Irrigation Efficiency
Calculation of irrigation water needs (NFR) can be done with the formula: NFR Rice = ETC + Pd + P + WLR -Re NFR palawija / sugar cane = ETC -Re ... Tertiary channel NFR / DR intake = (NFR (rice / secondary crops)) / Eff According in general water losses in irrigation networks can be divided as follows. a. 12.5% -20% in tertiary channels b. 5% -10% in the secondary channel c. 5% -10% in the primary canal Efficiency in each plot is estimated as follows:  Efficiency values in primary plots ranged from 92.5% -87.5%. Taken 90%  Efficiency values in secondary plots ranged from 92.5% -87.5%. Taken 90%  Efficiency values in tertiary plots range from 85% -77.5%. Taken 80% In the calculation of irrigation water requirements for rice, the calculation of the most efficient planting pattern is used, which is the alternative planting pattern of 14 in February 1. NFR Rice = (3,034 x 1.0) + (12,967 x 0) + (2.0 x 1.0) + (3,333   In this graph it can be stated that in February I was the time when the maximum irrigation water needs was tertiary NFR plots = 1.40 ltr / sec / ha and DR intake = 1.72 ltr / sec / ha. Whereas in August II and September I with the results of tertiary NFR plots = -0.02 ltr / sec / ha and DR intake = -0.03 ltr / sec / ha which means surplus water, so that no irrigation is needed.

Mainstay Debit Calculations
The data or assumptions used in the FJ Mock calculation are: A. 10-year Rainfall Data with rainfall stations which are considered to represent the condition of the area. The data needed is: a) d average: 10-year average rainfall b) n: Average number of 10 annual rainy days Calculates the average rainfall and the number of 10 yearly average rainy days in the Depati Parbo area in January.    .53 lt / sec The probability of being fulfilled is set at 80% (the possibility that the river discharge is lower than the main discharge is 20%). That possibility uses calculation k) Q mainstay 80% = (0.8 x Mainstay Debit) / (area DI) ltr / sec / ha = 0.8 x 71323.53 / 473 = 120.63 liter / sec / ha The graph above shows 80% Mainstay Debit for irrigation (Q80) which shows the availability of abundant water and can be used more optimally for community needs other than irrigation in the Pauh Tinggi area with maximum results in November Q80 = 160.31 ltr / sec / ha, and the minimum in August with Q80 = 91.18 liters / sec / ha.

Planting Patterns and Water Balance
Planting pattern is the most important way in planting system planning. The purpose of holding a planting system is to set the time, place, type and area of plants in the irrigation area. The purpose of the planting system is to utilize the irrigation water supply as effectively and efficiently as possible so that the plants can grow well. The biggest factor in cropping patterns can be said to be efficient and optimal is if the water needs are fulfilled by a reliable discharge (water balance). The following is the calculation of the water balance in the alternative cropping pattern from January 14 to I. Note: Mainstay 80% Q = 120.63 liter / sec / ha DR intake = 1.60 ltr / sec / ha Water balance = Q mainstay 80% -DR intake = 120.63 -1.60 = 119.03 ltr / dt.ha (fulfilled) In this final project 17 alternative cropping patterns are made, and based on the water balance, alternative cropping patterns 14 are displayed which are the most efficient and optimal planting system. Other alternative cropping patterns that have been made are attached to the Appendix.

Netto Debit
To determine the dimensions of the channel, the planned capacity is calculated against the maximum discharge Q = 100% x Maximum. The calculated discharge is based on the results of the alternative planting pattern 14 and in January to I. Qnetto = (NFR x A) / Eff = (NFR tertiary channel / DR intake) x A Hope Jaya Jaya Secondary Channel and Irrigation Building BHJ 3 are known with: Tertiary channel NFR = 1.30 ltr / sec / ha A tertiary plot of AK ki = 45 ha A tertiary plot of AK ka = 19.60 ha