Findings and analyses from the target case studies

Floodwater management in DG Khan spate irrigation system is guided by a set of formally documented key water distribution rules (Table 3). These rules have been instrumental in curtailing excessive upstream floodwater diversion, reducing flood damage, safeguarding downstream water supply and facilitating timely O&M. The fields entitled to irrigation are defined and mapped. The farmers cannot increase the size of their delineated irrigated areas even if there are excessive floods. The upstream priority is limited to a single turn of about 1000 mm irrigation depth from small floods. The large floods that often cause damage in the upstream section are allowed to travel to the downstream cultivable land where they are more easily harnessed for productive use.

Table 3. Key water distribution rules in DG Khan FBLS in Pakistan described during the FGDs and confirmed to be operational by all individually interviewed farmers

There is a functional collaborative institutional arrangement between the local government (Irrigation Department) and community-level Water Users’ Associations (WUAs). The local government is more actively involved in the upstream areas where there is not a well-established WUA to ensure that the water distribution rules are observed and there is no excessive upstream floodwater use (Fig. 2). In the midstream and downstream areas this responsibility is largely fulfilled by the respective WUAs with the support of the local government.

Fig. 2. Perceived responsibility per farmer group about the institutional responsibility for managing floodwater distribution in DG Khan spate irrigation system in Pakistan.

Source: Individual interviews.

The Irrigation Department has experienced technical staff who oversee O&M needs. They receive funding through government budget allocations and contributions from the farming communities. The general arrangement is that the farming and herding communities cover 60% of the routine O&M costs such as silt and weed clearance (in cash, labor or both) and 10–20% of major infrastructural repair or new developments. The adequately implemented O&M activities have contributed to several environmental benefits including mitigation of floodwater damage to agricultural land, enhanced soil moisture retention and decreased soil fertility depletion. The priority crops are wheat and sorghum, followed by beans. New crops will not be entitled to floodwater supply unless their introduction has been discussed and agreed upon among the Irrigation Department and the WUAs.

The floodwater management situation in the Tana River flood inundation system is sharply different. The only operational upstream first rule gives absolute priority to the upstream irrigating farmers. The rule does not specify the irrigation depth and turns—the upstream decide when the floodwater should flow to the downstream predominantly small-scale farmers that account for about two-third of the farming population. Rules on small and large floods, crop preferences and those that facilitate O&M are non-existent in Tana River. The institutional arrangement is also weak. Unlike in the DG Khan system there are no full-fledged WUAs but field-level committees of 20–30 farmers exist that manage floodwater sharing along the same field canal. Several of these field-level committees are not active—nearly two-third, about half and a third of the interviewed upstream, midstream and downstream farmers respectively never participated in their respective committee meetings (Fig. 3).

Fig. 3. Level of engagement of the Tana River flood-dependent farmers in irrigation committees. Usually, the committees convene four times annually.

Source: Individual interviews.

The lack of institutional maturity in Tana River despite being twice as old system as Fogera can be attributed to three factors. First, unlike in Fogera, there have not been any major external interventions that facilitated or motivated farmers to organize themselves. Government authorities largely ignored Tana River FBLS as they considered it a marginal agricultural system. Secondly, small-scale farmers have more pressing issues, such as ensuring sufficient harvest to feed their families. Finally, the large-scale farmers did not see the urgency to organize themselves as they have not been as severely affected by floodwater scarcity as the small-scale farmers.

In Fogera floodplain, the floodwater management is mainly governed by the upstream first rule, but unlike in the Tana River, the rule defines the irrigation depth and turn. Prior to the introduction of upstream commercial rice, a decade back by the local government, the rule granted the then maize and teff upstream farmers the priority for a single irrigation turn of 350 mm depth, and a second turn only after all the other fields secure the same single turn. This upstream priority irrigation depth was doubled following the introduction of rice to meet the high irrigation demand of the crop, estimated at 1000 mm for Fogera rice varieties (FAO, 2019). As a result, floodwater supply to the now downstream maize and teff crops has reduced by about 50%.

There is a strong functional institutional arrangement in the Fogera floodplain built on long-term collaboration between water-masters (farmer leaders) highly respected by the community and a legally powerful local administration. This collaborative engagement supported with hefty, yet graduated sanctions, has achieved a high degree of enforcement of the upstream first rule and successfully facilitated wide participation of the farming community in collective O&M activities. The water-masters are empowered and legally supported by the local administration to sanction first and second time violations of the upstream first rule or for failure to contribute to O&M by fines of 10 and 25 euros, respectively. Repetitive offenses could lead to deprivation of floodwater supply. A group of three to five water-masters represent 200–600 farmers in their respective villages. They do not receive salary, but in recognition of their service, they are entitled to priority irrigation.

The comprehensiveness of the water distribution rules and the strength of the enforcing institutions can explain the significantly better system-wide water distribution in DG Khan (Fig. 4). As gathered from the individual interviews, nearly 57% of the Tana River downstream farmers experienced water scarcity in 3 out of 5 yr when floodwater supply was not physically limiting—the corresponding value in DG Khan was 18%. Moreover, 10% of the Tana River downstream farmers did not have access to adequate floodwater supply in 4 out of 5 yr and 9% throughout the 5-yr period.

Fig. 4. Comparative assessment of floodwater scarcity experienced by Pakistani and Kenyan farmers in the past 5 flood season years when floodwater has not been physically limiting.

Source: Interview data.

The relatively low floodwater scarcity condition in DG Khan is particularly significant given the fact that the flood-irrigated areas in the downstream (651 ha) and the midstream (722 ha) are nearly triple that in the upstream (260 ha) (Fig. 5). Both upstream and midstream farmers occasionally divert large floods in violation of the rule on ‘small and large floods’. However, large floods are less destructive and can be more successfully harnessed midstream, explaining why midstream farmers manage to irrigate the highest share (85%) of total available land.

Fig. 5. Comparison of system-wide (upstream to downstream) flood irrigated areas in the DG Khan spate irrigation scheme in Pakistan. The data were gathered in 2021 and according to the interviewed farmers the irrigated area values are representative of the situation in the most frequent average flood season that occurs in 4 out of 5 yr.

Source: Individual interviews.

Complementary analyses from other FBLS

While scientific studies are limited, there are some documented cases that further illustrate the above presented impacts of water distribution rules and institutional arrangements on floodwater management and distribution. Below we provide four relevant examples.

The first example concerns Wadi Mawr spate irrigation system in Yemen. The predominant upstream first rule combined with the absence of demarcation and crop preference rules (Table 3) encouraged upstream expansion of the profitable, but highly water demanding banana plantation resulting in significant downstream floodwater supply reduction (Zenebe et al., Reference Zenebe, van Steenbergen, Newaz and Wegelin2016).

In the second example, the Wadi Siham spate irrigation system in Yemen, there is a ‘rule on small and large floods’ as defined in Table 3. Following modernization intervention, the multiple offtake system that allowed downstream water users to withdraw water directly from the wadi was replaced with a single upstream concrete distribution offtake. This gave more physical floodwater control to the upstream and led to frequent violation of the rule depriving the downstream of large floods (Mehari et al., Reference Mehari, van Steenbergen, Schultz, van Koppen, Giordano and Butterworth2007). As in Tana River, the Wadi Siham downstream farmers are not organized into WUAs and do not have adequate institutional capacity to collectively safeguard their floodwater supply entitlement (van Steenbergen et al., Reference van Steenbergen, Lawrence, Mehari, Salman and Faurès2010). DG Khan has a markedly different experience and situation than Wadi Siham. Infrastructural improvement interventions resulted in a multiple offtake system and the downstream receive their floodwater supply through direct diversion from the ephemeral river system. They do not hence rely on upstream canals and structures. The downstream farmers are well organized while the government (Irrigation Department) actively supports enforcement of water distribution rules. As a result, the downstream floodwater entitlements are largely respected.

Thirdly, Malota and Mchenga (Reference Malota and Mchenga2020) extensively discuss, albeit on a qualitative basis, that introducing a comprehensive set of water distribution rules is critical to address the upstream–downstream floodwater sharing challenges in the Malawi Shire Valley flood recession agriculture.

Finally, Shah et al. (Reference Shah, van Koppen, Merrey, de Lange and Samad2002) confirm that collaborative institutional arrangements between farmers and irrigation agencies (this is the case in DG Khan and Fogera) often result in effective water management systems, as: (a) usually, neither the farmers nor the irrigation agencies are on their own capable of meeting the financial resources required for O&M; and (b) farmers alone often do not invest into long-term sustainability of irrigation systems—a role that can be fulfilled by the public institutions.

Findings and analyses from the target case studies

The majority of the interviewed farmers across the three target case studies identified water management and distribution rules as having significant impact on their crop productivity.

In the DG Khan spate irrigation system, nearly 70% of the upstream and midstream farmers and about 80% of the downstream farmers ranked the key set of water distribution rules (Table 3) as the second most important factor contributing to their crop productivity, after physical floodwater availability. Agricultural inputs came a distant third followed by lack of adequate financial capacities to, for instance, timely cultivate the irrigable land; soil degradation; water logging and salinity problems.

The crop yield data collected in 2021 from the 105 interviewed DG Khan farmers are displayed in Figure 6. As confirmed during the individual interviews and FGDs, 2021 was characterized as an average flood season with a 4 in 5 yr occurrence. Figure 6 illustrates the positive impact of the water distribution rules on system-wide crop productivity: (a) the median upstream and midstream wheat yields are basically the same and that of the downstream is only 5% less; and (b) the midstream and downstream sorghum farmers each managed nearly 80% of the upstream farmers’ median yield. This is a significant achievement given the skewed distribution of flood-irrigated areas (see Fig. 5).

Fig. 6. Boxplot of the system-wide (upstream to downstream) productivity of the major crops in DG Khan spate irrigation system. The median, the line cutting across the box, is the center value of the database. The lower and upper edges of the box display the yields higher than a quarter and three quarters of the dataset while the highest and lowest data-points of the whiskers (lines) represent the maximum and minimum yields respectively.

Source: Interview data.

In the case of beans, the upstream–downstream median yield difference is very significant at about 43%, and moreover downstream farmers are concentrated on the lower yield range (Fig. 6). Beans are grown as a second crop after either wheat or sorghum harvests. The field bund heights in DG Khan are about 1 m and while some downstream farmers receive one full irrigation turn (1000 mm), most manage about 750 mm. Midstream fields receive 1000 mm while most upstream fields harness some 1500 mm. The net irrigation requirement of wheat and sorghum is about 550 mm while that of beans is 300 mm (FAO, 2020). Therefore, after the wheat or sorghum irrigation demands are satisfied, there will be sufficient residual moisture for bean production in the upstream and midstream areas, but a deficit of at least 100 mm or about a third of the demand in the downstream. Beans are sensitive to water stress. Field experiments conducted in arid and semi-arid regions found that a 25% irrigation deficit resulted in an average 30% beans yield reduction (Rai et al., Reference Rai, Sharma and Heitholt2020).

Although median yields of the DG Khan spate-irrigated fields are higher than the country-wide average by about 20% (wheat), 60–70% (sorghum) and 40–60% (beans); they are about two-thirds of the 3500 (wheat) and 6000 kg ha⁻¹ (sorghum) maximum yields obtained when irrigation and farming practices are not limiting (FAO, 2019). This yield gap is not primarily caused by floodwater supply scarcity, but rather due to impurity of seeds, poor land preparation and weed management and insufficient fertilizer application. Even if we assume a quarter of the 750–1000 mm irrigation depth received by downstream fields is lost due to flood damage to field intakes or breaching of field bunds, the wheat and sorghum water requirements would still be adequately met. The deep silty loam soils have a high water holding and capillary capacity making soil moisture readily available to the sorghum and wheat roots which grow to well below 1.5 m depth (Mehari et al., Reference Mehari, Schultz, Depeweg and De Laat2008).

In Tana River, the system-wide agricultural productivity gap is significantly bigger than that in DG Khan. Upstream median rice yield is higher by a third and two-thirds as compared to the midstream and downstream, respectively (Fig. 7). Likewise, upstream maize productivity is nearly 20 and 44% higher than the respective midstream and downstream yields, respectively. Primarily due to inadequate floodwater supply, just a quarter of the downstream managed to cultivate the high irrigation demanding rice crop and they mainly produced maize to cover their household needs. By contrast, nearly two-thirds and four in five of the midstream and upstream farmers harvested rice for commercial purposes and maize as the second crop for home consumption.

Fig. 7. Boxplot of the system-wide (upstream to downstream) productivity of the major crops under Tana River flood inundation system. The median, the line dividing the box, is the midpoint value of the yield dataset. The lower and upper margins of the box represent the yields higher than 25 and 75% of the dataset. The top and bottom values of the whiskers are the maximum and minimum yields.

Source: Interview data.

All the interviewed Tana River downstream farmers attributed their poor harvests to the upstream first water distribution rule—the only operational rule—that empowers the upstream to divert as much floodwater as they want. This view is shared by 40% of the midstream farmers. On the other hand, nearly all the upstream farmers and 60% of the midstream farmers identified inadequate field water management structures as the major limiting factors for agricultural productivity. This very problem is also acknowledged by nearly half of the downstream farmers. Unlike in DG Khan where gabion or concrete re-enforced flood resilient field water distribution intakes are in operation (van Steenbergen, Reference van Steenbergen1997; Mehari et al., Reference Mehari, Schultz and Depeweg2005), Tana River farmers rely on earthen structures that are more frequently susceptible to flood damage resulting in substantial floodwater losses.

The acute floodwater supply shortage faced by the downstream Tana River farmers is reflected in the rice yield of a quarter of the maximum attainable 9000 kg ha⁻¹ (FAO, 2019). That said, the best harvest by the upstream Tana farmers that often enjoy 1500 mm irrigation depth (rice requires 1000 mm) is also just 50% of the maximum achievable value. This is mainly due to significant floodwater losses. Moreover, nearly 40% of the interviewed upstream farmers reported pests and diseases incidences. This most probably is caused by excessive flooding and prolonged wet conditions as the problem is reported by only 3 and 5% of the midstream and downstream farmers, respectively. Finally, inadequate farming practices could have played a role. Tana River farmers practice direct broadcast sowing, which results in high planting density, low germination rate and poor seed setting (Zenebe et al., Reference Zenebe, Fleskens, Ritsema and van Steenbergen2022). Field experiments conducted in several perennial irrigation systems in Kenya (Ndiiri et al., Reference Ndiiri, Mati, Home, Odongo and Uphoff2013) and in Mali FBLS (Traore et al., Reference Traore, Traore, Synnevåg and Aune2020) established that a farming system that combines transplanting of younger seedlings and wider spacing can increase rice productivity by up to 40%. As Tana River FBLS has not been subject to any internal or external improvement interventions—neither improved field water management structures nor better farming practices have been introduced.

In Fogera floodplain, nearly all (95%) of the interviewed downstream farmers explained that the modified upstream first rule that doubled the priority entitlement of the upstream rice cultivation to two irrigation turns (about 700 mm) is the main factor for the decline of their teff and maize yields by approximately 15 and 33%, respectively (Fig. 8). Under the modified rule, the farmers explained that receiving a single turn (about 350 mm) is their best-case scenario. This irrigation depth, if efficiently utilized, would be sufficient for teff, but it is far below the maize requirement estimated at 650 mm (FAO, 2020).

Fig. 8. Boxplot of system-wide (upstream to downstream) productivity of the Fogera floodplain major crops under the traditional (pre-rice era) and the modified (post-rice period) water distribution rule. The median, the line dissecting the box, divides the yield dataset into two equal parts. The lower and upper edges of the box display the yields greater than 25 and 75% of the dataset while the whiskers indicate the minimum and maximum yields respectively.

Source: Interview data.

The median maize productivity under the traditional water distribution rule when the downstream fields often managed two turns (Fig. 8) was also low at about 64 and 55% of the corresponding Ethiopia country average (4327 kg ha⁻¹) and maximum (6000 kg ha⁻¹) attainable yields (Cochrane and Bekele, Reference Cochrane and Bekele2018; FAO, 2020). The significant, up to 40% floodwater losses, reported by farmers due to frequent flood damage to the weak earthen field water distribution structures, is the main contributing factor here. The intervention in Fogera that introduced upstream rice cultivation did not invest into gabion or concrete re-enforced field water management structures.

The median upstream Fogera rice yield is about 20% lower than that in the Tana River FBLS (Figs. 7 and 8). This is largely because unlike in the Tana River, the upstream first rule in Fogera limits the rice fields’ priority irrigation to 700 mm, which is 30% below the optimum requirement. In addition, the Fogera rice productivity shares the two main challenges faced in Tana River: (1) substantial floodwater losses; and (2) the non-optimal direct broadcast sowing-based farming system.

Complementary analyses from other FBLS

The upstream favoring water distribution rules that curtailed downstream floodwater supply across the earlier discussed Wadi Mawr and Wadi Siham cases also resulted in significant negative impacts on agricultural productivity.

Wadi Mawr spate irrigation system embodies the challenges of both Tana River (predominantly upstream first rule) and Fogera (upstream expansion of high-water demanding crop). The combined effect was that the downstream area became confined to subsistence sorghum cultivation characterized by frequent crop failures (Mehari et al., Reference Mehari, van Steenbergen and Schultz2011; van Steenbergen et al., Reference van Steenbergen, Nawaz, Aria, Karim, Tamim Kashifi, Zenebe and Roein2016). In Wadi Siham, despite the existence of the rule on ‘small and large floods’, the upstream farmers are irrigating as much as they want as is the case in Tana River. As a result, the downstream sorghum productivity fluctuates between 500 and 1000 kg ha⁻¹ (van Steenbergen et al., Reference van Steenbergen, Lawrence, Mehari, Salman and Faurès2010).